y=x(x+1)(x+2)(x+3)
y'=(x+1)(x+2)(x+3)+x(x+2)(x+3)+x(x+1)(x+3)+x(x+1)(x+2)
y'(0)= (1)(2)(3) =6
y'=(x+1)(x+2)(x+3)+x(x+2)(x+3)+x(x+1)(x+2)
y'|(x=0)=6
y′=(ⅹ+1)(x+2)(x+3)+x(x+2)(x+3)+x(ⅹ+1)(ⅹ+3)+x(x+1)(x+2)
∴x=0时,y'=1×2×3=6
一一一一一一一
整体性
y′=(x+1)(x+2)(x+3)+ⅹ[(x+1)(x+2)(ⅹ+3)]′
∴x=0时,y′=6
=6