x+y-1的绝对值+（x-y+3)²=0
所以
x+y-1=0
x-y+3=0
所以
x+y=1
x-y=-3
所以x²-y²
=(x+y)(x-y)
=1×(-3)
=-3
我要出去一下了,大概七点三刻左右再上