已知m²-mn=12,mn-n²=-15,求式子m²-n²与m²-2mn+n²的值
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![已知m²-mn=12,mn-n²=-15,求式子m²-n²与m²-2mn+n²的值](/uploads/image/z/3016322-26-2.jpg?t=%E5%B7%B2%E7%9F%A5m%26%23178%3B-mn%3D12%2Cmn-n%26%23178%3B%3D-15%2C%E6%B1%82%E5%BC%8F%E5%AD%90m%26%23178%3B-n%26%23178%3B%E4%B8%8Em%26%23178%3B-2mn%2Bn%26%23178%3B%E7%9A%84%E5%80%BC)
已知m²-mn=12,mn-n²=-15,求式子m²-n²与m²-2mn+n²的值
已知m²-mn=12,mn-n²=-15,求式子m²-n²与m²-2mn+n²的值
已知m²-mn=12,mn-n²=-15,求式子m²-n²与m²-2mn+n²的值
m²-n²
=m²-mn+mn-n²
=12-15
=-3
m²-2mn+n²
=m²-mn-mn+n²
=(m²-mn)-(mn-n²)
=12+15
=27
两式相加,m平方-n平方=12-15=-3 两式相减,即得m平方-2mn-n平方=12+15=27