Question

如果f'(2)=1,则limf(2-h)-f(2)/h=?

Answer 1

f'(2)=lim(f(2+h)-f(2))/h)=1

h=-h

lim(f(2-h)-f(2))/-h)=1

-lim((f(2-h)-f(2))/h)=1

lim((f(2-h)-f(2))/h)=-1

答案是-1