（x+1- __1_）÷(x- x² )
1-x x-1
=（x+1+ _1___）÷(x- x² )
x-1 x-1
=（x²-1+ 1__）÷(x² -x - x² )
x-1 x-1 x-1 x-1
=( x²-1+1）÷(x² -x - x² )
x-1 x-1
=( x² ）÷( -x )
x-1 x-1
=( x² ）×( x-1 )
x-1 -x
=-x