用换元法把1/（X平方＋2X+1）＋1/（X平方＋2X+2）＝2
设_X^2+2X+1＝Y,则原方程可化为_1/Y+1/[Y+1]=2
Y=[X+1]^2>=0
1/Y+1/[Y+1]=2
Y+1+Y=2[Y^2+Y]
2Y^2=1
Y^2=1/2
Y=2^(-1/2)
[x+1]^2=2^(-1/2)
x+1=+/-2^(-1/4)
x1=-1+2^(-1/4)
x2=-1-2^(-1/4)