Question

若f'(1)=3,则lim_(h->0)(f(1)-f(1-2h))/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