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先化简再求值(1-1\x+2)/x^2+2x+1\x^2-4.其中x=3
题目详情
先化简再求值(1-1\x+2)/x^2+2x+1\x^2-4.其中x=3
▼优质解答
答案和解析
[1-1/(x+2)]/[(x^2+2x+1)/(x^2-4)]
=[(x+2-1)/(x+2)]/[(x+1)^2/(x-2)(x+2)]
=[(x+1)/(x+2)]/[(x+1)^2/(x-2)(x+2)]
=(x+1)/(x+2)*(x-2)(x+2)/(x+1)^2
=(x-2)/(x+1)
=(3-2)/(3+1)
=1/4
=[(x+2-1)/(x+2)]/[(x+1)^2/(x-2)(x+2)]
=[(x+1)/(x+2)]/[(x+1)^2/(x-2)(x+2)]
=(x+1)/(x+2)*(x-2)(x+2)/(x+1)^2
=(x-2)/(x+1)
=(3-2)/(3+1)
=1/4
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