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问题: 若(x+y-3)+绝对值x-y+5=0,则x^2-y^2=????

解答:

因为(x+y-3)+ ︳x-y+5︱=0,所以x+y-3=0, ︳x-y+5 ︱=0
解方程组得,x+y=3 x-y=-5 x=-1 y=4
x^2-y^2=(-1)^2-(-4)^2=-15