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(m-n/2m+2n)-m²+n²/m²-n²

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(m-n/2m+2n)-m²+n²/m²-n²
计算 反正答案是-m+n/2m-2n
(m-n/2m+2n)-m²+n²/m²-n²
(m-n)/{2m+2n} - (m²+n²)/(m²-n²)
= (m-n)/{2(m+n)} - (m²+n²)/{(m+n)(m-n)}
= { (m-n)² - (m²+n²)/{2(m+n)(m-n)}
= {m²+n² -2mn - 2(m²+n²)/{2(m+n)(m-n)}
= { -2mn - (m²+n²)/{2(m+n)(m-n)}
= - (m+n)²/{2(m+n)(m-n)}
= - (m+n)/{2(m-n)}
= - (m+n)/(2m-2n)