(x的平方-1分之x的平方-2x+1+x分之1)除以x+1分之1
=((x-1)^2/(x-1)(x+1) +1/x) *(x+1)
=((x-1)/(x+1) +1/x) *(x+1)
=(x-1) +(x+1)/x
=x-1+1+1/x
=x+ 1/x