f(x)在x=a处可导,求lim(x趋近于a) f(x)-f(a)/a-x=?

Question

如题所述

Answer 1

lim(x->a) [f(x) - f(a] / (a - x)
= -lim(x->a) * [f(x) - f(a)] / (x - a),这是导数的定义
= -f'(a)