suppose that f is differentiable at a and f(a) is not equal to 0.

show that for h sufficiently small f(a+h) is not equal to zero and using the definition of a derivative directly, prove that 1/(f(x)) is differentiable at x=a and

(1/f)'(a) = -f'(a)/f^2(a)

stuck on this one anyone have any ideas? is the second part just plug and chug?