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Which of the following differential equations are of order 2 and degree 1?

(A). ddx(dydx)+xdydx=y\frac{d}{dx}\left(\frac{dy}{dx}\right) + x\frac{dy}{dx} = y

(B). d2ydx2+x=dydx−y\frac{d^2y}{dx^2} + x = \sqrt{\frac{dy}{dx} - y}

(C). (dydx)2+d2ydx2=log⁡x\left(\frac{dy}{dx}\right)^2 + \frac{d^2y}{dx^2} = \log x

(D). (dydx)2+dydx=3\left(\frac{dy}{dx}\right)^2 + \frac{dy}{{dx}} = 3

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 1

(A) becomes y′′+xy′=yy''+xy'=y: order 2, degree 1.

(B) on squaring gives (y′′+x)2=y′−y(y''+x)^2 = y'-y: degree 2.

(C) (y′)2+y′′=log⁡x(y')^2+y''=\log x: highest derivative y′′y'' has power 1, so order 2, degree 1.

(D) is order 1.

Hence only (A) and (C).

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