对数求导法y=x(x+1)(x+2)(x+3) *若用 对数求导法则：y'/y=1/【x(x+1)(x+2)(x+3)】*当x=0时,由*式子知道,y=0 带入#式子,y'=0但是

y=x(x+1)(x+2)(x+3)
lny=lnx +ln(x+1) +ln(x+2) +ln(x+3)
y'/y=(1/x) +(1/(x+1)) +(1/(x+2)) +(1/(x+3))
y'=y*((1/x) +(1/(x+1)) +(1/(x+2)) +(1/(x+3)))
=x(x+1)(x+2)+x(x+1)(x+3)++x(x+2)(x+3)+(x+1)(x+2)(x+3)
当x=0时，y'=1*2*3=6

一楼正解

y=x(x+1)(x+2)(x+3) 在这里我们可以用对数求导；但是必须满足一个条件.即y不等于0,否则不能两边取对数.你做得题就是没有讨论这种情况.应该这样解（1）当y不等于0时,两边取对数.lny=lnx +ln(x+1) +ln(x+2) +ln(x+3)y'...

y'/y=1/x+1/(x+1)+1/(x+2)+1/(x+3)
when x=0,
y--->6x
then put y to the right, you can get the answer.