Mathematics

Problem

Let

y=f(u)

and

u=g(x)

be differentiable functions. Which of the following relations is correct when expressing

\dfrac{dy}{dx}

entirely in Leibniz notation? a)

\displaystyle\frac{dy}{dx}=\frac{dy}{du}+\frac{du}{dx}

\displaystyle\frac{dy}{dx}=\frac{du}{dy}\cdot\frac{dx}{du}

\displaystyle\frac{dy}{dx}=\frac{dy}{du}\cdot\frac{du}{dx}

\displaystyle\frac{dy}{dx}=\frac{dy}{dx}\cdot\frac{du}{dx}