(X+1分之x-1+x平方-1分之2x）/x平方-1分之1
=[(x-1)/(x+1)+2x/(x+1)(x-1)]/[1/(x+1)(x-1)]
={[(x-1)^2+2x]/(x+1)(x-1)}*(x+1)(x-1)
=x^2-2x+1+2x
=x^2+1