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Q.The order and degree of the differential equation d dx(ey) = 0 respectively are 1
(A) 0, 1
(B) 1, 1
(C) 2, 1
(D) 1, not defined

CBSECBSE Class XII Board 2026MCQ· 1mImportance★★★★★
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The given equation ddx(ey)=0\frac{d}{dx}(e^y)=0 simplifies to eydydx=0e^y \frac{dy}{dx}=0, which is a first-order differential equation. Since ey≠0e^y \neq 0, the highest derivative is dydx\frac{dy}{dx} raised to the power 1, so the degree is 1. The correct option is (B).

The order of a differential equation is the highest order derivative present. The degree is the power of the highest order derivative, provided the equation is polynomial in derivatives. Here, the equation looks deceptively simple — but we must first expand it properly.

  1. Expand the derivative. The given equation is ddx(ey)=0\frac{d}{dx}(e^y) = 0. Using the chain rule:

ddx(ey)=ey⋅dydx.\frac{d}{dx}(e^y) = e^y \cdot \frac{dy}{dx}.

So the equation becomes:

eydydx=0.e^y \frac{dy}{dx} = 0.

  1. Identify the highest derivative.

    The only derivative present is dydx\frac{dy}{dx}, which is a first derivative. Hence the order is 11.

  2. Determine the degree.

    The degree is defined only when the differential equation is a polynomial in the derivatives. Here, the term eye^y is not a polynomial in yy or its derivatives — it's an exponential function of yy. However, the derivative dydx\frac{dy}{dx} itself appears with power 1, and the equation is already in the form ey⋅dydx=0e^y \cdot \frac{dy}{dx} = 0.

    Since eye^y is never zero for any real yy, we can divide both sides by eye^y to get:

dydx=0.\frac{dy}{dx} = 0.

This is a polynomial in dydx\frac{dy}{dx} (specifically, it is (dydx)1=0\left(\frac{dy}{dx}\right)^1 = 0). So the degree is 11. …

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