(x+y-3)二次方 +(x-y+5)二次方 =0,x方-y方=?

问题描述:

(x+y-3)二次方 +(x-y+5)二次方 =0,x方-y方=?

(x+y-3)二次方 +(x-y+5)二次方 =0
因为平方数都是大于等于0,和为0,则:
x+y-3=0
x-y+5=0
x+y=3
x-y=-5
所以:
x²-y²
=(x+y)(x-y)
=3•(-5)
=-15