Question

若f'(1)=3,则lim_(h->0)(f(1+h)-f(1)/h= ( )

Answer 1

lim_(h->0)(f(1)-f(1-2h))/h =lim_(h->0)2*(f(1)-f(1-2h))/2h =2*lim_(h->0)(f(1)-f(1-2h))/2h =2*f'(1)=2*3=6