How do you use this notation?
If I have
$\displaystyle f(x)=x^3+5x^2+4$
How do you wright this?
Since $\displaystyle f(x)=x^3+5x^2+4$, just make y = f(x) so y = $\displaystyle x^3+5x^2+4$.
dy/dx = f'(x).
dy/dx means derivative of y with respect to x.
d/dx is the derivative with respect to x. If you have $\displaystyle \frac{d}{dx}x^3+5x^2+4$ then you just take the derivative of that.