Mathematics · Class 12 Science
Ch 4Theory of Equations — Class 12 Mathematics, concept-first.
By this point you have solved linear equations, and quadratic equations and inequations, in real depth — including, from the previous chapter, the exact relationship between a quadratic's two roots and its coefficients .
Key concepts
Hover a concept to preview it and jump to its most relevant Q&A.
Theory of Equations
This chapter builds a general toolkit for degree-n polynomial equations: how the coefficients encode the sum and products of the roots, how to exploit extra clues about the roots (equal roots, roots in a fixed ratio, etc…
Most relevant Q&A
- If $1, 1, \alpha$ are the roots of $x^3 - 6x^2 + 9x - 4 = 0$, then find $\alpha$.Preview
- Solve the equation: $6x^6 - 25x^5 + 31x^4 - 31x^2 + 25x - 6 = 0$.Preview
- If the product of the roots of $4x^3 + 16x^2 - 9x - a = 0$ is 9, then find a.Preview
- Solve $18x^3 + 81x^2 + 121x + 60 = 0$, given that one root is equal to half the sum of the remaining roots.Preview
- If the product of the roots of $4x^3 + 16x^2 - 9x - a = 0$ is 9, then find 'a'.Preview
Chapter contents
The NCERT structure, section by section. Open a section to see its questions, then read the concept-first solution.
Introduction
By this point you have solved linear equations, and quadratic equations and inequations, in real depth — including, from the previous chapter, the exact relationship between a quadratic's two roots an…
Polynomial Equations and the Remainder Theorem
A polynomial equation of degree has the form , with . Up to now you have solved linear and quadratic equations directly, but most equations that show up in real applications — in engineering, economic…
Relations Between the Roots and the Coefficients
Write the general monic degree- equation as and let be its roots. Comparing this with the factored form and expanding, the coefficient of each power of turns out to be (up to a sign) one of the elemen…
Symmetric Functions of the Roots
A symmetric function of the roots is any expression built from that is unchanged if you permute the roots among themselves — for instance , , or for a cubic.
Synthetic Division and Solving Equations Using Extra Root Conditions
Dividing a polynomial by using the Remainder Theorem's coefficient pattern is called synthetic division — a compact bookkeeping scheme that avoids writing out the full long division.
Multiple Roots
A root of is said to have multiplicity if divides exactly but does not — equivalently, appears times among the roots counted in the Fundamental Theorem of Algebra.
Complex and Irrational Roots Occur in Conjugate Pairs
Two useful “pairing” facts restrict what the roots of an equation can look like, depending on what kind of coefficients the equation has.
Transformation of Equations
Sometimes the most efficient way to solve or analyse an equation is not to attack it directly, but to transform it into a related equation whose roots are a known function of the original roots (shift…
Reciprocal Equations
A polynomial is called reciprocal, and the equation a reciprocal equation, if its coefficient sequence read forwards is the same as read backwards, either exactly or up to an overall sign flip.
Sample & Board Papers
Sample papers and previous-year board questions for this subject.
+−Show 16 questionsHide questions16 questions
- Q1If $1, 1, \alpha$ are the roots of $x^3 - 6x^2 + 9x - 4 = 0$, then find $\alpha$.Preview
- Q2Solve the equation: $6x^6 - 25x^5 + 31x^4 - 31x^2 + 25x - 6 = 0$.Preview
- Q3If the product of the roots of $4x^3 + 16x^2 - 9x - a = 0$ is 9, then find a.Preview
- Q4Solve $18x^3 + 81x^2 + 121x + 60 = 0$, given that one root is equal to half the sum of the remaining roots.Preview
- Q5If the product of the roots of $4x^3 + 16x^2 - 9x - a = 0$ is 9, then find 'a'.Preview
- Q6Solve $4x^3 - 24x^2 + 23x + 18 = 0$, given that the roots of this equation are in arithmetic progression.Preview
- Q7If the product of the roots of $4x^3 + 16x^2 - 9x - a = 0$ is $9$, then find $a$.Preview
- Q8Solve the equation $x^5 - 5x^4 + 9x^3 - 9x^2 + 5x - 1 = 0$.Preview
- Q9Form the quadratic equation whose roots are $\dfrac{p-q}{p+q}$, $-\dfrac{(p+q)}{p-q}$ $(p \neq \pm q)$.Preview
- Q10Find the algebraic equation whose roots are 2 times the roots of $x^5 - 2x^4 + 3x^3 - 2x^2 + 4x + 3 = 0$.Preview
- Q11Solve the equation $x^4 + 2x^3 - 5x^2 + 6x + 2 = 0$ given that $1+i$ is one of its roots.Preview
- Q12Find the transformed equation whose roots are the negatives of the roots of $x^4+5x^3+11x+3=0$.Preview
- Q13Solve the equation $x^4+2x^3-5x^2+6x+2=0$ given that $1+i$ is one of its roots.Preview
- Q14If $1, 1, \alpha$ are the roots of $x^3 - 6x^2 + 9x - 4 = 0$, then find $\alpha$.Preview
- Q15Solve $x^4 + 4x^3 - 2x^2 - 12x + 9 = 0$, given that it has two pairs of equal roots.Preview
- Q16Solve the equation $x^4 + 2x^3 - 5x^2 + 6x + 2 = 0$, given that $1 + i$ is one of its roots.Preview