y=(x^2+2x+2)/(x+1)
=((x+1)^2+1)/(x+1)
=(x+1)+1/(x+1)
x+1>0時,(x+1)+1/(x+1)≥2√[(x+1)*1/(x+1)]=2,
x+1<0時,-(x+1) >0,
-(x+1)-1/(x+1)≥2√[-(x+1)*-1/(x+1)]=2,
所以(x+1)+1/(x+1)≤-2.
函數(shù)值域是（-∞,-2]∪[2,+∞）.x+1>0時，(x+1)+1/(x+1)≥2√[(x+1)*1/(x+1)]=2,為什么大于等于號后面有根號這里利用的是基本不等式：a+b≥2√(ab),后面當(dāng)然有根號。