Mathematics 9709 · AS & A Level · Differential equations

Differential equations — practice question

(a)[1]

For $y = \ln(\ln x)$, show that $\frac{dy}{dx} = \frac{1}{x\ln x}$.

(b)[7]

The variables $x$ and $t$ are linked by the differential equation $x\ln x + t\frac{dx}{dt} = 0$. It is given that $x = e$ when $t = 2$. Solve the differential equation to find $x$ in terms of $t$, and simplify your result.

(c)[1]

Therefore state what happens to the value of $x$ as $t$ approaches infinity.

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