已知:x+y=-½,x-y=-7/2,求x-2(1/4x-1/3y²)+(-3/2x+1/3y²)的值

已知:x+y=-½,x-y=-7/2,求x-2(1/4x-1/3y²)+(-3/2x+1/3y²)的值
已知:x+y=-½,x-y=-7/2,求x-2(1/4x-1/3y²)+(-3/2x+1/3y²)的值

已知:x+y=-½,x-y=-7/2,求x-2(1/4x-1/3y²)+(-3/2x+1/3y²)的值
x-2(1/4x-1/3y²)+(-3/2x+1/3y²)
=x-1/2x+2/3y²-3/2x+1/3y²
= -x+y²
由已知联立方程组,得 x+y=-1/2
x-y=-7/2
解得 x=-2
y=3/2
∴当 x=-2,y=3/2时,
原式=-（-2）+（3/2）²=2+9/4=17/4

x-2(1/4x-1/3y²)+(-3/2x+1/3y²)
=x-1/2x+2/3y²-3/2x+1/3y²
=-x+y²
x+y=-1/2 x-y=-7/2可得x=-4 y=3/2
带入
4+9/4=25/4x+y=-1/2 x-y=-7/2可得x=-4 y=3/2这不太清楚，到底怎么得出来的解错了。。应该...

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x-2(1/4x-1/3y²)+(-3/2x+1/3y²)
=x-1/2x+2/3y²-3/2x+1/3y²
=-x+y²
x+y=-1/2 x-y=-7/2可得x=-4 y=3/2
带入
4+9/4=25/4

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