y'=[x/(x+1)]'=[x'(x+1)-x(x+1)']/(x+1)²=1/(x+1)²
曲线在点P的切线斜率为1
1/(x+1)²=1
(x+1)²=1
x+1=1或x+1=-1
x=0或x=-2
x=0代入y=x/(x+1),解得y=0
x=-2代入y=x/(x+1) y=-2/(-2+1)=2
点P坐标为(0,0)或(-2,2)