(x^2+x)/(x^2+3x+2)=0
x^2+x=0,且x^2+3x+2≠0
x(x+1)=0,且(x+1)(x+2)≠0
x=0,或-1,且x≠-1,-2
∴x=0
1/(x-1)^2=1/(0-1)^2=1