(2mx^2-x^2+3x+1)-(5x^2-4y^2+3x)
=(2m-1-5)x^2+1+4y^2
值与x无关
则x^2的系数为0
所以2m-6=0
m=3
2m^3-[3m^2+(4m-5)+m]
=2m^3-3m^2-5m+5
=2*27-3*9-5*3+5
=17