有條1985年mc唔識

用戶10012

2008-10-01 5:20 am

✔ 最佳答案

2/(1 + x) - 2/(1-x) - 4x/(x^2 - 1)
= 2/(1 +x) - 2/(1-x) - 4x/[(1+ x)(x -1)]
= 2/(1+x) + 2/(x -1) - 4x/[(1+x)(x -1)]
= [2(x -1) + 2( 1 +x) - 4x]/[(1 + x)(x -1)]
= (2x - 2 + 2 + 2x - 4x)/[(1+x)(x-1)]
= 0.
probably there is some mistake in the question, please check.

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Chun Hin

2008-10-01 11:39 pm

2/(1 + x) - 2/(1-x) - 4x/(x^2 - 1)
= 2/(1 +x) - 2/(1-x) - 4x/[(1+ x)(x -1)]
= 2/(1+x) + 2/(x -1) - 4x/[(1+x)(x -1)]
= [2(x -1) + 2( 1 +x) - 4x]/[(1 + x)(x -1)]
= (2x - 2 + 2 + 2x - 4x)/[(1+x)(x-1)]
= 0.

There are some mistakes.

參考: my maths knowledge

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