若(x+y-3)²+(x-y+5)²=0,则x²-y²的值是这是一个选择题,A 8 B -8 C 15 D -15
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若(x+y-3)²+(x-y+5)²=0,则x²-y²的值是这是一个选择题,A 8 B -8 C 15 D -15
若(x+y-3)²+(x-y+5)²=0,则x²-y²的值是
这是一个选择题,A 8 B -8 C 15 D -15
若(x+y-3)²+(x-y+5)²=0,则x²-y²的值是这是一个选择题,A 8 B -8 C 15 D -15
(x+y-3)²+(x-y+5)²=0
x+y-3=0 x-y +5=0
解出来:
x= -1
y = 4
则x²-y²
= 1 -16= -15
有什么不明白可以对该题继续追问
请及时选为满意答案,
选D
根据平方为非负数得
x+y-3=0 x-y+5=0
x+y=3 x-y=-5
x²-y²=(x+y)(x-y)=3*(-5)=-15