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先化简再求值:(x-2)/(x方+4x+4)+x/(4-x方),求当x=3时的值
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人气:370 ℃ 时间:2020-10-02 00:20:22
解答
(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...
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