已知a²-ab=50,ab-b²=30,求代数式a²-b²和a²-2ab+b²的值
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已知a²-ab=50,ab-b²=30,求代数式a²-b²和a²-2ab+b²的值
已知a²-ab=50,ab-b²=30,求代数式a²-b²和a²-2ab+b²的值
已知a²-ab=50,ab-b²=30,求代数式a²-b²和a²-2ab+b²的值
a²-ab=50,ab-b²=30,
a²-b²
=a²-ab+ab-b²
=50+30
=80
a²-2ab+b²
=a²-ab-ab+b²
=a²-ab-(ab-b²)
=50-30
=20
80 20 。。。。。。。。。。。
a²-b²=80,(a-b)^2=20
a²-ab=50 ①
ab-b²=30 ②
①+②得a²-b²=80
①-②得a²-2ab+b²=20