a²-b²= (a+b)²-2ab
=6×6-3×2
=30
(5ab+4a+7b)+(6a-3ab)-(4ab-3b)
=5ab+4a+7b+6a-3ab-4ab+3b
=10a+10b+5ab-7ab
=10(a+b)-2ab
=10×6-2×3
=54
已知a+b=6,ab=3求a²-b²= (5ab+4a+7b)+(6a-3ab)-(4ab-3b)=
已知a+b=6,ab=3求a²-b²= (5ab+4a+7b)+(6a-3ab)-(4ab-3b)=
数学人气:276 ℃时间:2020-04-03 11:46:43
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