By using the definition of derivative, find the derivatives of the following
functions.
a) f (x) = 4 − x^2
b) f (x) =(1 − x)/(2x)

You can define the derivative of a curve as its gradient at a certain point. I'll do the first one as an example:

f(x)=4x^0-x^2
\frac{dy}{dx}= (0)4x^{-1} - (2)x^1
\frac{dy}{dx}= -2x

See what I've done? I multiplied each term by the power of x and then reduced the power of x by one.

Hope it helped. If you need more help, don't hesitate to post.