已知a²-2ab=-4,b²-2ab=5,求a²-b²的值
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已知a²-2ab=-4,b²-2ab=5,求a²-b²的值
已知a²-2ab=-4,b²-2ab=5,求a²-b²的值
已知a²-2ab=-4,b²-2ab=5,求a²-b²的值
a²-b²
=a²-2ab-( b²-2ab)
=-4-5
=-9
相减,得
a²-b²=-4-5=-9
a²-2ab=-4 ①
b²-2ab=5 ②
①-②得:a²-b²=-9