先化简再求值:(x-2)/(x方+4x+4)+x/(4-x方),求当x=3时的值
问题描述：
先化简再求值:(x-2)/(x方+4x+4)+x/(4-x方),求当x=3时的值
快!
答
(x-2)/(x方+4x+4)+x/(4-x方),=(x-2)/(x+2)²-x/(x+2)(x-2)=[(x-2)²-x(x+2)]/(x+2)²(x-2)=（x²-4x+4-x²-2x）/(x+2)²(x-2)=(-6x+4)/(x+2)²(x-2) ==(-6x3+4)/(3+2)²(3-2)=-14/2...