已知XY=5,(X-Y)²=16,求:(1)X²+Y²   (2)X+Y

问题描述:

已知XY=5,(X-Y)²=16,求:(1)X²+Y²   (2)X+Y
 

x^2+y^2=(x-y)²+2xy=16+10=26
(x+y)^2=(x-y)²+4xy=16+20=36
所以x+y=6,-6