若多項式(2mx²;-x²;=5x+8)-(5x²;-3y=5x)的值與x的取值無關,求m³;-(2m²;-(5m-4)+m)的值

若多項式(2mx²;-x²;=5x+8)-(5x²;-3y=5x)的值與x的取值無關,求m³;-(2m²;-(5m-4)+m)的值

題目應是:若多項式(2mx²;-x²;+5x+8)-(5x²;-3y+5x)的值與x的取值無關,求m³;-(2m²;-(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多項式的值與x的取值無關,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