已知x+y=6,xy=4,则x2+y2=_;(x-y)2=_.

问题描述:

已知x+y=6,xy=4,则x2+y2=______;(x-y)2=______.

∵x+y=6,xy=4,
∴x2+y2=(x+y)2-2xy=62-2×4=28;
(x-y)2=(x+y)2-4xy=62-4×4=20.
故答案为28;20.