y=(1+x)(2+x)(3+x)=(x²+3x+2)(x+3)求导y'=[(x²+3x+2)]'(x+3)+(x²+3x+2)(x+3)'=(2x+3)(x+3)+(x²+3x+2)=2x²+9x+9+x²+3x+2=3x²+12x+11