若多项式(2mx^2-x^2+5x+8)-(5x^2-3y+5x)的值与x的取值无关,求m^3-[2m^2-(5m-4)+m]的值.

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若多项式(2mx^2-x^2+5x+8)-(5x^2-3y+5x)的值与x的取值无关,求m^3-[2m^2-(5m-4)+m]的值.
若多项式(2mx^2-x^2+5x+8)-(5x^2-3y+5x)的值与x的取值无关,求m^3-[2m^2-(5m-4)+m]的值.

若多项式(2mx^2-x^2+5x+8)-(5x^2-3y+5x)的值与x的取值无关,求m^3-[2m^2-(5m-4)+m]的值.
(2mx^2-x^2+5x+8)-(5x^2-3y+5x)
=2mx^2-x^2+5x+8-5x^2+3y-5x
=2mx^2-6x^2+8+3y
=2(m-3)x^2+3y+8 的值与x的取值无关,所以 m-3=0,m=3
m^3-[2m^2-(5m-4)+m]
=m^3-(2m^2-5m+4+m)
=m^3-2m^2+5m-4-m
=m^3-2m^2+4m-4
=3^3-2x3^2+4x3-4
=17

当x=0时,多项式=8+3y
当x=1时,多项式=2m-1+5+8-5+3y-5
=2m+2+3y
值与x的取值无关
∴2m+2+3y=8+3y
∴m=3
∴m^3-(2m^2-(5m-4)+m)=27-【(18-11)+3】=17

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