(1-1/x+1)除以x/x^2-1 =(x/(x+1))/(x/(x+1)(x-1))=x-1
x/x-2-3/x+2=1
x(x+2)-3(x-2)=(x+2)(x-2)
x^2+4x-3x+6=x^2-4
x=-10