已知x+y=5,xy=3.求:(1)x2+y2(2)(x-y)2-数学

题目简介

已知x+y=5,xy=3.求:(1)x2+y2(2)(x-y)2-数学

题目详情

已知x+y=5,xy=3.
求:(1)x2+y2(2)(x-y)2
题型:解答题难度:中档来源:不详

答案

(1)x2+y2=x2+y2+2xy-2xy,
=(x+y)2-2xy,
=25-6,
=19;

(2)(x-y)2=x2+y2+2xy-4xy,
=(x+y)2-4xy,
=25-12,
=13.

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