Question

mostrar pela definição f(x) = -18 f'(x) =0

Answer 1

$f'(x)= \lim_{\Delta x \to 0} \frac{f(\Delta x+ h)-f(x)}{\Delta x} \\\\f'(x)= \lim_{\Delta x \to 0} \frac{-18-(-18)}{\Delta x}\\\\ f'(x)= \lim_{\Delta x \to 0} \frac{0}{\Delta x} \\\\f'(x)= \lim_{\Delta x \to 0} 0\\\\f'(x)=0$