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If x=log⁡etx=\log_e t and y=1ty=\dfrac{1}{t}, then d2ydx2\dfrac{d^2y}{dx^2} at t=0.1t=0.1 is

Solution

✅ Correct Option: 2

dxdt=1t\dfrac{dx}{dt} = \dfrac{1}{t} and dydt=−1t2\dfrac{dy}{dt} = -\dfrac{1}{t^2}, so dydx=−1t\dfrac{dy}{dx} = -\dfrac{1}{t}.

Then d2ydx2=ddt(−1t)/dxdt=1/t21/t=1t\dfrac{d^2y}{dx^2} = \dfrac{d}{dt}\left(-\dfrac{1}{t}\right)\Big/\dfrac{dx}{dt} = \dfrac{1/t^2}{1/t} = \dfrac{1}{t}.

At t=0.1t=0.1 this is 10.

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