已知a+b=6,ab=2.(1)求a²+b²的值:(2)求(a-b)²的值
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已知a+b=6,ab=2.(1)求a²+b²的值:(2)求(a-b)²的值
已知a+b=6,ab=2.(1)求a²+b²的值:(2)求(a-b)²的值
已知a+b=6,ab=2.(1)求a²+b²的值:(2)求(a-b)²的值
a²+b²
=(a+b)²-2ab
=6²-2×2
=32
(a-b)²
=(a+b)²-4ab
=6²-4×2
=28
整体代入法:
⑴a^2+b^2=(a+b)^2-2ab=36-4=32,
⑵(a-b)^2=(a+b)^2-4ab=36-8=28.