已知m+n=9,mn=14,求3m2+3n2的值.
人气:117 ℃ 时间:2019-08-22 10:56:52
解答
将m+n=9两边平方得:(m+n)2=m2+n2+2mn=81,
把mn=14代入得:m2+n2=53,
则原式=3×53=159.
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