导数的四则运算法则
(1)[u(x)±v(x)]'=u'(x)±v'(x);
(2)[u(x)*v(x)]'=u'(x)v(x)+u(x)v'(x);
(3)[Cu(x)]'=Cu'(x)（C为常数）;
(4)[u(x)/v(x)]'=[u'(x)v(x)-u(x)v'(x)]/v平方(x)（v(x)≠0）