已知(3x+1)(3x-3)-3x+2)^2=-7,(y+7)(y-7)-y(y-7)=0,求8y^2-5y(-y+3x)+4y(-4y-5/2x)的值

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已知(3x+1)(3x-3)-3x+2)^2=-7,(y+7)(y-7)-y(y-7)=0,求8y^2-5y(-y+3x)+4y(-4y-5/2x)的值已知(3x+1)(3x-3)-3x+2)^2=-

已知(3x+1)(3x-3)-3x+2)^2=-7,(y+7)(y-7)-y(y-7)=0,求8y^2-5y(-y+3x)+4y(-4y-5/2x)的值
已知(3x+1)(3x-3)-3x+2)^2=-7,(y+7)(y-7)-y(y-7)=0,求8y^2-5y(-y+3x)+4y(-4y-5/2x)的值

已知(3x+1)(3x-3)-3x+2)^2=-7,(y+7)(y-7)-y(y-7)=0,求8y^2-5y(-y+3x)+4y(-4y-5/2x)的值
(3x+1)(3x-3)-(3x+2)^2
=9x^2-6x-3-(9x^2+12x+4)
=-18x-7=-7
∴ x=0
(y+7)(y-7)-y(y-7)
=y^2-49-y^2+7y
=7y-49=0
∴ y=7
8y^2-5y(-y+3x)+4y(-4y-5/2x)
=8y^2+5y^2-15xy-16y^2-10xy
=-3y^2-25xy
=-3*7*7-0
=-147

缺半个括弧，没法算

解得x=0,y=7
将原式代入x=0进行化简
原式=-3y^2=-147

有不明白的地方再问哟，祝你学习进步，更上一层楼！ (*^__^*)

把x=0 y=7带入就可以了

(3x+1)(3x-3)-3x+2)^2=-7 这个写错了吧

(3x+1)(3x-3)-(3x+2)^2=-7
9x^2-6x-3-9x^2-12x-4=-7
-18x-7=-7
18x=0
x=0

(y+7)(y-7)-y(y-7)=0,
y^2-49-y^2+7y=0
7y=49
y=7

8y^2-5y(-y+3x)+4y(-4y-5/2x)
=8y^2+5y^2-15xy-16y^2-10xy
=-3y^2-25xy
=-3x7^2
=-147

x=0
要求的式子x在分母，这不是没意思了吗?

(3x+1)(3x-3)-(3x+2)^2
=9x^2-6x-3-(9x^2+12x+4)
=-18x-7=-7
∴ x=0

(y+7)(y-7)-y(y-7)
=y^2-49-y^2+7y
=7y-49=0
∴ y=7

8y^2-5y(-y+3x)+4y(-4y-5/2x)
=8y^2+5y^2-15xy-16y^2-10xy
=-3y^2-25xy
=-3*7*7-0
=-147

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