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If x=at2x = at^2 and y=a3t3y = a^3 t^3, then d2ydx2\frac{d^2 y}{dx^2} will be :

Solution

✅ Correct Option: 3

dxdt=2at\frac{dx}{dt} = 2at, dydt=3a3t2\frac{dy}{dt} = 3a^3 t^2.

dydx=3a3t22at=3a2t2\frac{dy}{dx} = \frac{3a^3 t^2}{2at} = \frac{3a^2 t}{2}.

d2ydx2=ddt(dydx)⋅dtdx=3a22⋅12at=3a4t\frac{d^2y}{dx^2} = \frac{d}{dt}\left(\frac{dy}{dx}\right) \cdot \frac{dt}{dx} = \frac{3a^2}{2} \cdot \frac{1}{2at} = \frac{3a}{4t}.

Note: Treating y=a3t3y = a^3 t^3 literally with cubic in a; if intended as y=at3y = at^3, the answer would differ.

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