若f'(X0)=2则lim【f(x0-k)-f(x0)}/2k

问题描述:

若f'(X0)=2则lim【f(x0-k)-f(x0)}/2k

令h=-k,则lim(k→0) [f(x0-k) - f(x0)] / (2k)=-1/2×lim(h→0) [f(x0+h) - f(x0)] /h=-1/2×f'(x0)=-1