1-x
解：
原式
=(x+2)/[(x+2)(x-2)]×(x-2)/(x+1)-A
=1/(x+1)-[2x(x+1)-(x²+2x)]/(x+1)
=1/(x+1)-x²/(x+1)
=(1-x²)/(x+1)
=(1+x)(1-x)/(x+1)
=1-x
