已知(a+b)²=11,ab=2,则（a-b）²的值是?

已知(a+b)²=11,ab=2,则（a-b）²的值是?
已知(a+b)²=11,ab=2,则（a-b）²的值是?

已知(a+b)²=11,ab=2,则（a-b）²的值是?
(a-b)²
=a²-2ab+b²
=(a²+2ab+b²)-4ab
=(a+b)²-4ab
=11-4×2
=11-8
=3
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