问题 选择题 y=xx-1的导数为( )A.-1(x-1)2B.1(x-1)2C.-2x-1(x-1)2D.2x-1(x-1)2 答案 y′=x′(x-1)-x(x-1)′(x-1)2=(x-1)-x(x-1)2=-1(x-1)2,故选A.