1、y=x^2 *log2(3x)求导得到y'=(x^2)' *log2(3x) +x^2 *[log2(3x)]'=2x *log2(3x) +x^2 * 3/ (3x *ln2)=2x *log2(3x) +x /ln22、y=cos(2x+1) /x求导得到y'= [cos(2x+1)' *x -cos(2x+1)] /x^2= [-2x *sin(2x+1) -cos(2x+1)] /x^2
