设f（x）=x+(x+1)(x+2）（x+3),则f（x）的导数是多少

df（x）=1dx+（x+2)(x+3)d(x+1)+(x+1)(x+3)d(x+2)+(x+1)(x+2)d(x+3)
=1dx+(x^2+5x+6)dx+(x^2+4x+3)dx+(x^2+3x+2)dx
=1dx+(3x^2+12x+11)dx=(3x^2+12x+12)dx
即导数是3*x^2+12x+12