已知x,y满足(x=y)的平方=1,(x-y)的平方=25,求x的平方+y的平方=xy的值
已知x,y满足(x=y)的平方=1,(x-y)的平方=25,求x的平方+y的平方=xy的值
数学人气:872 ℃时间:2020-05-05 11:23:57
优质解答
(x+y)²=1x²+y²+2xy=1(x-y)²=25x²+y²-2xy=25相加2(x²+y²)=26x²+y²=13xy=[1-(x²+y²)]/2=-6所以x²+y²+xy=7
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