已知x+y=3,xy=1,求:(1)x²+y²(2)(x-y)²的值

问题描述:

已知x+y=3,xy=1,求:(1)x²+y²(2)(x-y)²的值

(1)x²+y²=(x+y)²-2xy
=9-2
=7
(2)(x-Y)²=x²-2xy+y²
=7-2xy
=7-2
=5