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已知(x+y)2=7,(x-y)2=3.求:(1)x2+y2的值;(2)x4+y4的值;(3)x6+y6的值.

题目详情
已知(x+y)2=7,(x-y)2=3.
求:(1)x2+y2的值;
(2)x4+y4的值;
(3)x6+y6的值.
▼优质解答
答案和解析
(1)∵(x+y)2=7,(x-y)2=3,
x2+2xy+y2=7,x2-2xy+y2=3,
∴x2+y2=5,xy=1;
(2)x4+y4=(x2+y22-2x2y2
=25-2
=23;
(3)x6+y6=(x2+y2)(x4-x2y2+y4
=5×(23-1)
=110.