已知m²-mn=7,mn-n²=-2,求m²-n²及m²-2mn+n²的值.
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![已知m²-mn=7,mn-n²=-2,求m²-n²及m²-2mn+n²的值.](/uploads/image/z/1811303-71-3.jpg?t=%E5%B7%B2%E7%9F%A5m%26%23178%3B-mn%3D7%2Cmn-n%26%23178%3B%3D-2%2C%E6%B1%82m%26%23178%3B-n%26%23178%3B%E5%8F%8Am%26%23178%3B-2mn%2Bn%26%23178%3B%E7%9A%84%E5%80%BC.)
已知m²-mn=7,mn-n²=-2,求m²-n²及m²-2mn+n²的值.
已知m²-mn=7,mn-n²=-2,求m²-n²及m²-2mn+n²的值.
已知m²-mn=7,mn-n²=-2,求m²-n²及m²-2mn+n²的值.
m²-n²
=m²-mn+mn-n²
=(m²-mn)+(mn-n²)
=7-2=5
m²-2mn+n²
=m²-mn-mn+n²
=(m²-mn)-(mn-n²)
=7-(-2)
=9
m的平方-n的平方=(m的平方-mn)+(mn-n的平方)=7+(-2)=5