x+1分之1 - x的平方-6x+9分之3-x * x-3分之x的平方+x等于多少?
问题描述：
x+1分之1 - x的平方-6x+9分之3-x * x-3分之x的平方+x等于多少?
其中x=根号2
答
原式=1/(x+1)*[(x-3)/(x+3)^2+2/(x+3)]-x/(x+3)(x-3)
=1/(x+1)[3(x+1)/(x+3)^2]-x/(x+3)(x-3)
=3/(x+3)^2-x/(x+3)(x-3)
=[3(x-3)-x(x+3)]/(x+3)^2(x-3)
=-(x^2+9)/(x+3)^2(x-3).