已知a-b=7,ab=2,求a²+b²和(a+b)²的值.
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已知a-b=7,ab=2,求a²+b²和(a+b)²的值.
已知a-b=7,ab=2,求a²+b²和(a+b)²的值.
已知a-b=7,ab=2,求a²+b²和(a+b)²的值.
a²+b²=(a-b)²+2ab=7²+2x2=53
(a+b)²=(a-b)²+4ab=7²+4x2=57
a²+b²=(a-b)²+2ab=49+4=53,
(a+b)²=(a-b)²+4ab=49+8=57.