Q.For each of the differential equations given below, indicate its order and degree (if defined).
Concept understanding — Order Of Differential Equation
Order of a Differential Equation
A differential equation involves an unknown function together with its derivatives dxdy,dx2d2y,dx3d3y,…. The order of the equation is simply the order of the highest derivative that appears in it.
So to find the order, scan the equation, find the most-differentiated term, and read off how many times y has been differentiated there.
Some examples
- dxdy+3y=0 — the highest derivative is the first derivative, so the order is 1.
- dx2d2y+5(dxdy)3+y=0 — the highest derivative present is dx2d2y, so the order is 2. (The cube on dxdy is a power, not a higher order.)
- (dx3d3y)2+dx2d2y=sinx — the highest is the third derivative, so the order is 3.
Do not confuse order with degree. Order = the order of the highest derivative present. Degree = the power of that highest-order derivative once the equation is written free of radicals and fractions in the derivatives. Raising a derivative to a power changes the degree, never the order.
Why order matters
The order tells you how many arbitrary constants the general solution will contain: a first-order equation gives a one-constant family, a second-order equation gives a two-constant family, and so on. Equivalently, it tells you how many initial or boundary conditions you need in order to pin down a single particular solution. Recognising the order is therefore the very first step in classifying and then solving a differential equation.
This is one of the very first ideas introduced in the NCERT Class 12 Differential Equations chapter, and questions on "order and degree of differential equation" are a near-certain fixture in CBSE board papers and JEE Main. Anyone searching "differential equation class 12 formula" should nail this classification step before moving to solving techniques, since it decides how many arbitrary constants the general solution will carry.
Concept: Order and Degree of a Differential Equation
Order = highest derivative present. Degree = power of the highest derivative after the equation is made polynomial in derivatives (if possible).
(i) dx2d2y+5x(dxdy)2−6y=logx
Highest derivative is dx2d2y, which appears to the first power. No radicals or non-polynomial terms affect it.
Order = 2, Degree = 1.
(ii) (dxdy)3−4(dxdy)2+7y=sinx
Highest derivative is dxdy, raised to power 3.
Order = 1, Degree = 3.
(iii) dx4d4y−sin(dx3d3y)=0
Highest derivative is dx4d4y, but the term sin(dx3d3y) is not a polynomial in the derivative — degree is not defined.
Order = 4, Degree = not defined.
- Order 2, degree 1;
- Order 1, degree 3;
- Order 4, degree not defined.
Order is the highest derivative present; degree is the power of that highest derivative after the equation is made polynomial in derivatives. (i) Order 2, degree 1.
(ii) Order 1, degree 3.
(iii) Order 4, degree not defined (due to sine of a derivative).
The two numbers — order and degree — are the simplest descriptors of a differential equation. Order is straightforward: it’s just the highest derivative that appears. Degree is trickier: it’s the exponent of that highest derivative after you’ve rewritten the equation so that all derivatives are raised to positive integer powers and no derivative is inside a transcendental function (like sin, cos, log, exp). If you can’t do that, degree is not defined.
Let’s apply this to each equation.
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Equation (i): dx2d2y+5x(dxdy)2−6y=logx
The highest derivative is dx2d2y — that’s order 2.
Now look at the equation: it’s already a polynomial in the derivatives. The term dx2d2y appears with exponent 1. There’s no sine, no log of a derivative, no fractional power. So the degree is simply 1.
TipThe logx on the right is a function of x alone, not of y or any derivative — it doesn’t affect the degree at all. Only derivatives matter.
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Equation (ii): (dxdy)3−4(dxdy)2+7y=sinx
The highest derivative is dxdy — order 1.
The equation is already a polynomial in that derivative: the term (dxdy)3 has exponent 3. No further manipulation is needed. So degree is 3.
Watch outA common mistake is to think the degree is the highest power among all terms — here someone might say 3 because of the cube, but that’s actually correct in this case. The real pitfall is when the highest derivative itself has a fractional power or is inside a function; then you must rationalise first.
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Equation (iii): dx4d4y−sin(dx3d3y)=0
The highest derivative is dx4d4y — order 4.
Now for degree: the equation contains sin(dx3d3y). That’s a transcendental function of a derivative. You cannot expand sin(u) as a finite polynomial in u — it’s an infinite series. So the equation cannot be written as a polynomial in the derivatives. Hence degree is not defined.
ImportantWhenever a derivative appears inside a trigonometric, logarithmic, exponential, or any non-polynomial function, the degree is not defined — regardless of the order.
- Order 2, degree 1.
- Order 1, degree 3.
- Order 4, degree not defined.
Method: Reading off order and degree
For any differential equation, order and degree are found by inspection using two clear rules.
Steps
Step 1: Find the order.
The order is the highest-order derivative that appears (the one with the most differentiations).
Step 2: Check the equation is polynomial in the derivatives.
Degree is defined only if every derivative appears with a whole-number power and no derivative sits inside a function like sin, log, e(⋅) or under a root.
Step 3: Read the degree.
If it is polynomial in the derivatives, the degree is the power of the highest-order derivative.
Step 4: Declare 'not defined' when needed.
If a derivative is wrapped in a transcendental function (e.g. sin(dx3d3y)), the degree is not defined — never expand it into a series.
Common Mistakes
Mistake 1: Taking the highest power of any derivative as the degree.
Why it's wrong: in (i), (dxdy)2 appears, but the degree is the power of the highest-order derivative dx2d2y, which is 1. Correct approach: degree looks only at the top-order derivative.
Mistake 2: Assigning a degree to (iii).
Why it's wrong: sin(dx3d3y) wraps a derivative in a transcendental function, so the equation is not polynomial in derivatives and the degree is not defined. Correct approach: state "degree not defined," never expand the sine.
Mistake 3: Miscounting the order.
Why it's wrong: the order is the highest derivative present — 4 in (iii), not 3. Correct approach: scan for the largest number of differentiations.
Showing the 12 most recent of 26 on this concept.
- AP EAPCET 2026Set eng-2026-05-15-FN1 markMCQQ.Among the following the differential equations, the equation having order 2 and degree 3 is (A) dxdy−siny=dx2d2y(dx2d2y−1) (B) (dx2d2y)3=dxdy+y2(dx3d3y)2 (C) (dx2d2y)3=(dx2d2y)3/2+x2 (D) dxdy−siny=(dx2d2y)3(dx2d2y−1)
›Reveal solutionSolution
Order is the highest derivative present; degree is the power of that highest derivative once the equation is made free of radicals/fractional powers involving derivatives. Only option (A) reduces to order 2, degree 3. Answer: (A).
Concept and Intuition
To find the degree of a differential equation, first make sure it is written as a polynomial in derivatives — any square roots, fractional powers, or derivatives inside denominators must be cleared first (by squaring, cubing, etc., as needed) before reading off the exponent of the highest-order derivative term.
Step-by-Step Solution
- Option (A): dxdy−siny=y′′y′′−1. Highest derivative: y′′ (order 2). Isolate the radical (already isolated) and square both sides: (dxdy−siny)2=(y′′)2(y′′−1)=(y′′)3−(y′′)2. This is polynomial in y′′ with highest power 3 — order 2, degree 3. ✓ Matches what's asked.
- Option (B): (y′′)3=y′+y2(y′′′)2. Highest derivative is y′′′ (order 3), appearing squared — order 3, degree 2. Does not match.
- Option (C): (y′′)3=(y′′)3/2+x2. Isolate the fractional power: (y′′)3−x2=(y′′)3/2; squaring: [(y′′)3−x2]2=(y′′)3, giving highest power (y′′)6 — order 2, degree 6. Does not match.
- Option (D): dxdy−siny=(y′′)3(y′′−1)=(y′′)7/2−(y′′)3. Isolating and squaring gives a degree of 7 in y′′ — order 2, degree 7. Does not match.
- Only (A) gives the required order 2, degree 3.
Common Mistakes
- Reading off the degree directly from the exponent of the outer term (e.g. treating the exponent "3" in y′′y′′−1 literally) without actually clearing the radical first.
- Confusing order (which derivative is highest) with degree (its power).
✓Final answerThe correct option is (A) — dxdy−siny=dx2d2y(dx2d2y−1).
ANSWER: A
- AP EAPCET 2022Set eng-2022-07-07-AN1 markMCQQ.If a and b are respectively the order and degree of a differential equation y2(y′′)2+3x(y′)1/3+x2y2=sinx, then (A) b=a (B) a=3b (C) b=3a (D) ab=6
›Reveal solutionSolution
Order is fixed by the highest derivative (y′′, so a=2); clearing the fractional power on y′ by cubing the whole equation raises the power of y′′ to 6=3a, giving b=3a.
Concept and Intuition
The order of a differential equation is simply the order of the highest derivative appearing. The degree is only defined once the equation is written as a polynomial in all the derivatives (integer, non-negative powers) — so any fractional or negative power on a derivative must first be cleared by an appropriate algebraic operation (like raising both sides to a power), and this operation can also change the power of other derivative terms present in the equation.
Step-by-Step Solution
- The equation is y2(y′′)2+3x(y′)1/3+x2y2=sinx.
- The highest-order derivative present is y′′ (second derivative), so the order a=2.
- The term (y′)1/3 has a fractional exponent, so the equation is not yet a polynomial in the derivatives.
- Isolate that term: 3x(y′)1/3=sinx−y2(y′′)2−x2y2.
- Cube both sides to clear the cube root: 27x3(y′)=[sinx−y2(y′′)2−x2y2]3.
- Expanding the cube, the term with the highest power of y′′ comes from cubing −y2(y′′)2 alone, giving −y6(y′′)6 — so y′′ now appears to the power 6.
- Hence the degree is b=6.
- Compare with a=2: b=3a since 3×2=6.
Common Mistakes
- Reading off the exponent 2 on (y′′)2 directly as the degree, without first checking whether the equation is already a polynomial in all derivatives (it isn't, because of the fractional-power y′ term).
- Forgetting that clearing one derivative's fractional power (via cubing the whole equation) also multiplies the exponent of every other derivative term by the same factor.
✓Final answerThe correct option is (C) — b=3a.
ANSWER: C
- AP EAPCET 2024Set eng-2024-05-19-AN1 markMCQQ.The difference of the order and degree of the differential equation (dx2d2y)−7/2(dx3d3y)2−(dx2d2y)−5/2(dx4d4y)=0 is (A) 5 (B) 3 (C) 4 (D) 2
›Reveal solutionSolution
Order =4, degree =1, so their difference is 4−1=3.
Concept and Intuition
The order of a differential equation is the order of its highest derivative. The degree is the power of the highest-order derivative once the equation is made a polynomial in all derivatives (free of fractional/negative exponents).
Step-by-Step Solution
- Highest derivative is dx4d4y so the order is 4.
- Multiply the whole equation by (dx2d2y)7/2 to remove negative fractional powers.
- First term: (dx3d3y)2; second term: (dx2d2y)1dx4d4y.
- The equation is now polynomial, with dx4d4y appearing to the first power, so degree =1.
- Difference =4−1=3.
Common Mistakes
- Reading degree directly from the fractional exponents without first clearing them.
- Taking the power 2 on d3y/dx3 as the degree — degree refers to the highest-order derivative.
✓Final answerThe correct option is (B) — 3.
ANSWER: B
NoteThis solution was worked out by our team and cross-checked by a second independent solve. The official answer key for this question could not be confirmed, so please cross-verify with the official paper where possible.
- AP EAPCET 2023Set eng-2023-05-17-AN1 markMCQQ.The order and degree of the differential equation 3x2dx2d2y−sin(dx3d3y)+cos(xy)=0 are (A) Order can't be defined and degree is 3 (B) Order is 3 and degree can't be defined (C) Order is 3 and degree is 1 (D) Order is 1 and degree is 3
›Reveal solutionSolution
Because the highest derivative y′′′ sits inside a sin(⋅), the equation is not a polynomial in derivatives, so its degree is undefined even though its order (3) is perfectly well defined.
Concept and Intuition
Order of a DE = order of the highest derivative appearing. Degree = the power of the highest-order derivative, but this is only defined when the equation, after clearing radicals/fractions, is a polynomial in all the derivatives. If the highest derivative appears inside a non-polynomial function (sin, log, exponential, etc.), degree simply cannot be assigned.
Step-by-Step Solution
- The DE is 3x2y′′−sin(y′′′)+cos(xy)=0.
- The highest-order derivative present is y′′′ (third derivative) — so the order is 3.
- However, y′′′ appears as the argument of sin(⋅), not raised to an integer power — this equation is not a polynomial in y′′′ (or any of the derivatives), even after any algebraic rearrangement, since sin cannot be turned into a finite polynomial expression in y′′′.
- Therefore the degree is not defined, while the order is 3.
Common Mistakes
- Assuming "the coefficient of the highest derivative is 1 inside sin" makes the degree 1 — degree requires a polynomial equation, and sin(y′′′) is transcendental in y′′′, not polynomial.
- Confusing which derivative sets the order — it's y′′′ (order 3), not y′′.
✓Final answerThe correct option is (B) — Order is 3 and degree can't be defined.
ANSWER: B
- AP EAPCET 2023Set eng-2023-05-15-FN1 markMCQQ.The order and degree of the differential equation (dx3d3y)1/2−2(dxdy)1/4+xy=0 are respectively (A) 3 and 12 (B) 3 and 2 (C) 3 and 4 (D) 3 and 6
›Reveal solutionSolution
The order is 3 (from the third derivative); after systematically squaring twice to clear all fractional exponents (the 1/2 power on y′′′ and the 1/4 power on y′), the equation becomes polynomial with y′′′ appearing to the 4th power — so degree =4.
Concept and Intuition
Order is simply the highest derivative present (here, the third derivative, so order 3). Degree requires the equation to first be made polynomial in all the derivatives (no fractional or negative powers, no derivatives inside radicals) — only then is the degree the power of the highest-order derivative. Since we have two different fractional powers (1/2 on y′′′ and 1/4 on y′), we must clear both, which can require squaring more than once and tracks a growing power on y′′′.
Step-by-Step Solution
-
Order: the highest derivative is dx3d3y, so order =3.
-
Clearing the fractional powers — write p=y′′′, q=y′, a=xy:
p1/2−2q1/4+a=0⟹p1/2=2q1/4−a
- Square once to remove the 1/2 power on p:
p=4q1/2−4aq1/4+a2
This still carries fractional powers of q (namely q1/2 and q1/4), which must also be cleared since all derivative terms must end up with integer powers, not just the highest one.
- Isolate the term with the highest remaining fractional power (q1/4), letting w=q1/4 (so q1/2=w2):
p−a2=4w2−4aw
This is a quadratic in w:
4w2−4aw−(p−a2)=0⟹w=2a±p
(after simplifying the quadratic formula, using a2+p−a2=p inside the root).
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Raise both sides to the 4th power to remove w=q1/4 entirely: q=(2a±p)4. Expanding and isolating the remaining p term, then squaring once more to eliminate it, produces a final polynomial equation in p alone (together with a,q) whose highest power of p=y′′′ is 4 — arising because the expansion of the 4th power creates a p2 term, and the final squaring step (needed to remove the leftover square root) doubles that to p4.
-
So after fully clearing all radicals, the equation is a polynomial of degree 4 in y′′′, while remaining order 3 (still only third derivatives appear, no higher).
Common Mistakes
- Stopping after the first squaring (thinking degree =2) and forgetting that the other fractional power (on y′) must also be cleared before degree is well-defined, since the standard convention requires the whole equation to be free of fractional/negative powers of derivatives.
- Confusing "order" (3, straightforward) with "degree" (which requires this careful algebraic clearing).
✓Final answerThe correct option is (C) — 3 and 4.
ANSWER: C
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- AP EAPCET 2023Set eng-2023-05-18-AN1 markMCQQ.The degree of the differential equation log(dxdy)=(2x+3dxdy)2 is (A) 1 (B) 2 (C) 3 (D) not defined
›Reveal solutionSolution
Because the derivative sits inside a transcendental function (a logarithm) rather than as a pure power, this differential equation has no polynomial form in dy/dx, so its degree is not defined.
Concept and Intuition
The "degree" of a differential equation is defined as the power of the highest-order derivative, but ONLY after the equation has been made free of radicals, fractional powers, and any derivative sitting inside a non-polynomial (transcendental) function such as log, sin, e(⋅), etc. If the derivative cannot be isolated as a polynomial term, degree is simply not defined — order is still defined (here order =1), but degree is not.
Step-by-Step Solution
- The equation is log(dxdy)=(2x+3dxdy)2.
- The highest derivative present is dxdy (order 1), but it appears inside a log(⋅) on the left side.
- There is no way to algebraically rearrange this into a polynomial equation in dxdy (the log cannot be removed without introducing an exponential of the RHS, which is not a polynomial either).
- Since the equation cannot be written as a polynomial in the derivatives, its degree is, by definition, not defined.
Common Mistakes
- Confusing "order" (which is well-defined here, =1) with "degree" (which is not).
- Trying to force a degree by looking only at the exponent "2" on the RHS while ignoring that the LHS derivative sits inside a log.
✓Final answerThe correct option is (D) — not defined.
ANSWER: D
- AP EAPCET 2024Set eng-2024-05-20-AN1 markMCQQ.Order and degree of the differential equation dx3d3y=[1+(dxdy)2]5/2 respectively are (A) 5,2 (B) 3,5 (C) 3,2 (D) 2,3
›Reveal solutionSolution
Order is the highest derivative present (3); degree requires clearing the fractional exponent first, which makes the highest derivative appear squared — giving order 3, degree 2: (C).
Concept and Intuition
"Order" of a differential equation is simply the order of the highest derivative appearing. "Degree" is the power of the highest-order derivative after the equation has been made a polynomial in derivatives (i.e., all fractional/negative powers of derivatives must first be cleared by algebraic manipulation such as squaring).
Step-by-Step Solution
- The highest derivative present is dx3d3y — a third-order derivative. So order =3.
- The RHS, [1+(dxdy)2]5/2, has a fractional exponent, so the equation is not yet in polynomial form.
- Square both sides to remove the fractional power: (dx3d3y)2=[1+(dxdy)2]5.
- Now the equation is polynomial in the derivatives, and the highest-order derivative dx3d3y appears to the power 2. So degree =2.
Common Mistakes
- Reading off the exponent 5/2 directly as the "degree" — degree is only defined after clearing fractional powers, not before.
- Confusing order (of the derivative) with degree (of the equation in that derivative).
✓Final answerThe correct option is (C) — 3, 2.
ANSWER: C
- AP EAPCET 2024Set eng-2024-05-20-FN1 markMCQQ.The sum of the order and degree of the differential equation dx4d4y={c+(dxdy)2}3/2 is (A) 4 (B) 6 (C) 5 (D) 8
›Reveal solutionSolution
Squaring both sides clears the 3/2 power, giving order 4 and degree 2; their sum is 6.
Concept and Intuition
Degree is only meaningful once the differential equation is written as a polynomial in all the derivatives involved — any radicals (fractional powers) on a derivative term must first be removed by an algebraic operation such as squaring, cubing, etc.
Step-by-Step Solution
- Given: dx4d4y={c+(dxdy)2}3/2.
- Square both sides to remove the 3/2 power: (dx4d4y)2={c+(dxdy)2}3.
- This is now a genuine polynomial equation in the derivatives y′′′′ and y′.
- Highest-order derivative: y′′′′=dx4d4y, so order =4.
- That highest-order derivative appears with power 2 on the left, so degree =2.
- Sum of order and degree =4+2=6.
Common Mistakes
- Reading the degree straight off the un-squared equation as 3/2 (degree must be a whole number, obtained only after clearing radicals).
- Miscounting the order as 1 by focusing on the dy/dx term instead of the highest derivative y′′′′.
✓Final answerThe correct option is (B) — 6.
ANSWER: B
- AP EAPCET 2021Set eng-2021-08-23-FN1 markMCQQ.The order and degree of the differential equation dxdy−4dxdy−7x=0 are respectively ______ (A) 1 & 21 (B) 2 & 1 (C) 1 & 1 (D) 1 & 2
›Reveal solutionSolution
Order is the highest derivative present; degree is the power of the highest derivative once the equation is rationalized (radical-free) in the derivatives.
Concept and Intuition
The order of a differential equation is simply the order of the highest derivative appearing in it. The degree is only defined once the equation is a polynomial in its derivatives (no radicals or fractional powers involving a derivative) — so before reading off the degree, we must first clear any such radical by squaring or otherwise rationalizing.
Step-by-Step Solution
- The equation is dxdy−4dxdy−7x=0.
- Only dy/dx (first derivative) appears — no d2y/dx2 or higher — so the order is 1.
- To find the degree, isolate the radical: dxdy=4dxdy+7x.
- Square both sides to remove the square root: dxdy=(4dxdy+7x)2.
- Expanding the right side gives a term 16(dxdy)2, so the highest power of dy/dx in this polynomial form is 2.
- Hence the degree is 2.
Common Mistakes
- Reading the degree directly off the original (un-rationalized) equation, which would incorrectly suggest a fractional degree of 1/2.
- Confusing order (count of the highest derivative) with degree (its power after rationalizing).
✓Final answerThe correct option is (D) — 1 & 2.
ANSWER: D
- AP EAPCET 2026Set eng-2026-05-14-AN1 markMCQQ.The order and degree of the differential equation {1+(dxdy)2}3/2=dx2d2y are respectively (A) 23,2 (B) 2,3 (C) 2,2 (D) 3,4
›Reveal solutionSolution
The order is the highest derivative present (y′′, order 2); the degree requires first clearing the fractional power by squaring, after which the highest derivative appears to the power 2 — so order and degree are both 2.
Concept and Intuition
The order of a differential equation is simply the order of the highest derivative appearing. The degree is the power of the highest-order derivative after the equation has been made a polynomial in all the derivatives (no fractional or negative powers of any derivative allowed) — so if a fractional power like 3/2 appears on an expression containing lower derivatives, you must algebraically clear it before reading off the degree.
Step-by-Step Solution
- The equation is {1+(dxdy)2}3/2=dx2d2y.
- The highest derivative present is dx2d2y — so the order is 2.
- The left side has a fractional exponent 3/2 on an expression involving dy/dx (not the highest derivative), so we cannot read the degree directly; we must eliminate the fractional power.
- Square both sides: {1+(dxdy)2}3=(dx2d2y)2.
- Now the equation is polynomial in all derivatives, and the highest-order derivative d2y/dx2 appears with power 2 — so the degree is 2.
Common Mistakes
- Reading off "degree 3/2" directly from the unsquared equation — degree must always be a positive integer, which is the signal that the equation needs to be rationalized first.
- Confusing order (highest derivative present) with degree (power of the highest derivative after rationalizing).
✓Final answerThe correct option is (C) — 2,2.
ANSWER: C
- AP EAPCET 2023Set eng-2023-05-17-AN1 markMCQQ.Let c1,c2,c3,c4 be arbitrary constants. The order of the differential equation, corresponding to y=c1ex+c2elogex+c3sin2x−c4(cos2x−1) is (A) 1 (B) 2 (C) 3 (D) 4
›Reveal solutionSolution
Simplifying the given expression shows c3 and c4 always appear only as the sum c3+c4, so there are really just 3 independent arbitrary constants, making the order of the corresponding DE equal to 3.
Concept and Intuition
The order of the differential equation satisfied by a family of curves equals the number of independent arbitrary constants in the family — not simply the number of symbols written. Redundant constants (ones that only ever appear combined) must be collapsed first.
Step-by-Step Solution
- Simplify elogex=x (for x>0).
- Simplify −c4(cos2x−1)=−c4(−sin2x)=c4sin2x.
- So y=c1ex+c2x+c3sin2x+c4sin2x=c1ex+c2x+(c3+c4)sin2x.
- Let C3=c3+c4 — a single arbitrary constant (since c3,c4 are both arbitrary, their sum is just another arbitrary constant, with no independent extra freedom).
- So the family is effectively y=c1ex+c2x+C3sin2x — exactly 3 independent arbitrary constants.
- Hence the order of the differential equation representing this family is 3.
Common Mistakes
- Counting 4 constants at face value without noticing c3,c4 collapse into one.
- Forgetting to simplify elogex to x first, which could obscure the constant-counting.
✓Final answerThe correct option is (C) — 3.
ANSWER: C
- AP EAPCET 2024Set eng-2024-05-22-FN1 markMCQQ.The sum of the order and degree of the differential equation x(dx2d2y)1/2=(1+dxdy)4/3 is (A) 5 (B) 8 (C) 12 (D) 10
›Reveal solutionSolution
Order and degree are only meaningful after the equation is made polynomial in its derivatives — that requires clearing the fractional exponents first. Answer: 5.
Concept and Intuition
The order of a differential equation is the order of the highest derivative present. The degree is the power of the highest-order derivative, but only after the equation has been rewritten as a polynomial in the derivatives (no fractional or negative powers of any derivative term). So before reading off the degree, any radicals or fractional exponents on derivative terms must be cleared.
Step-by-Step Solution
- Given: x(dx2d2y)1/2=(1+dxdy)4/3.
- The highest derivative present is y′′=dx2d2y, so the order is 2.
- To clear the fractional powers 21 and 34, raise both sides to the power 6 (the LCM of denominators 2 and 3): x6(y′′)3=(1+y′)8.
- Now the equation is polynomial in derivatives, and the highest-order derivative y′′ appears to the power 3 — so the degree is 3.
- Sum of order and degree: 2+3=5.
Common Mistakes
- Reading off the degree directly from the un-cleared equation (e.g., taking the exponent 1/2 as the "degree"), which is invalid since degree must be a non-negative integer from a polynomial form.
- Using an incorrect LCM (e.g., raising to the 3rd or 2nd power alone) and failing to fully clear both fractional exponents simultaneously.
✓Final answerThe correct option is (A) — 5.
ANSWER: A
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