已知:a-b=7.a的平方减b的平方=56.求ab的值?
快
人气:215 ℃ 时间:2020-04-05 02:57:34
解答
a-b=7.a^2-b^2=56
a^2-b^2=(a-b)(a+b)=56
a+b=8
ab=[(a+b)^2-(a-b)^2]/4=(64-49)/4=15/4
或解出a=15/2,b=1/2
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