X-Y=2,X²-Y²=10求X²+Y²
4个回答
X²-Y²=(X+Y)(X-Y)=10
X-Y=2
则X+Y=5
平方
X²-2XY+Y²=4
X²+2XY+Y²=25
相加
2(X²+Y²)=29
X²+Y²=29/2
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