已知x(x-1)-(x²-y)=-2，求(x² y²)／2-xy的值
已知x(x-1)-(x²-y)=-2，求(x² y²)／2-xy的值
解：
去括号，x²-x-x²+y=-2
化简，得-x+y=-2
两边乘以-1，得：x-y=2
(x²+y²)/2-xy
=(x²-2xy+y²)/2（通分）
=(x-y)²/2
=(2)²/2
=2
已知X（X-1）-（X²一y）=-2，求X²+y²/2-Xy的值
X（X-1）-（X²一y）=-2
x²-x-x²+y=-2
∴-x+y=-2
即x-y=2
(x²+y²)/2-xy
=1/2(x²+y²-2xy)
=1/2(x-y)²
=2²÷2
=2
已知x(x-1)-(x²-y)=-6，求x²+y²/2-xy的值
x(x-1)-(x²-y)=-6
整理可得：x-y=6
两边平方：（x-y）²=36
x²+y²-2xy=36
x²+y²=36+2xy
（x²+y²）/2-xy
=（36+2xy）/2-xy
=18+xy-xy
=18
已知x(x+1)-(x²+y）=-3,求（x²＋y²）÷2-xy的值
x(x+1)-(x²+y）=-3
x²+x-x²-y=-3
x-y=-3
所以原式=(x²+y²-2xy)/2
=(x-y)²/2
=9/2
已知：x（x-1）-（x²-y）=﹣2 求2分之x²+y²-xy的值
已知：x（x-1）-（x²-y）=﹣2
那么x-y=2
所以½(x²+y²)-xy=(x²+y²-2xy)/2=(x-y)²/2=2²/2=2
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已知x(x-1)-(x²-y)=-3,求x²+y²-2xy的值.
x(x-1)-(x²-y)=-3
x²-x-x²+y=-3
-x+y=-3
x-y=3
x²+y²-2xy
=(x-y)²
=3²
=9
先化简再求值 已知x(x-1)-(x²-y0=-2,求x²+y²÷2-xy的值
即想²-x-x²+y=-2
-x+y=-2
x-y=2
所以原式=(x²+y²-2xy)/2
=(x-y)²/2
=4/2
=2
已知x﹙x-1﹚-﹙x²-y﹚=-2,求x²+y²／2-xy的值（需过程）——初二数学
x﹙x-1﹚-﹙x²-y﹚=-2
x²-x-x²+y=-2
x-y=2
x²+y²／2-xy
=1/2*x²+1/2(x²-2xy+y²)
=1/2(x-y)²+1/2*x²
=1/2×2²+1/2*x²
=2 +1/2*x²
=
已知x(x-1)-(x²-y)=3,求（2分之x²+y²）-xy的值
即x²-x-x²+y=3
-x+y=3
x-y=-3
所以原式=(x²-2xy+y²)/2
=(x-y)²/2
=9/2
设x(x-1)-(x²-y)=-2,求(x²+y²)/2-xy
x(x-1)-(x²-y)=-2
x²-x-x²+y=-2
y-x=-2
(y-x)²=4
x²+y²-2xy=4
x²+y²=4+2xy
(x²+y²)/2-xy
=(4+2xy)/2-xy
=2+xy-xy
=2
