Question

已知：x（x-1)-(x2-y)= 4,求0.5(x2+y2)-xy的ŀ

Answer 1

配成x-y平方式

所求值=8

方法如下

Answer 2

你好

x（x-1)-(x²--y)= 4
x²-x-x²+y=4
y-x=4
0.5(x²+y²)-xy
=0.5[(x²+y²)-2xy]
=0.5（x-y）²
=0.5（y-x）²
=0.5*16
=8

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