若代数式m²X+2nX-X²+b+X的值与;字母X的取值无关求3m²-1/2n³-m²n+4n³+5 /2n³

若代数式m²X+2nX-X²+b+X的值与;字母X的取值无关求3m²-1/2n³-m²n+4n³+5 /2n³
若代数式m²X+2nX-X²+b+X的值与;字母X的取值无关
求3m²-1/2n³-m²n+4n³+5 /2n³

若代数式m²X+2nX-X²+b+X的值与;字母X的取值无关求3m²-1/2n³-m²n+4n³+5 /2n³
题目有误,应该是：代数式mX²+2nX-X²+b+X的值与;字母X的取值无关
mX²+2nX-X²+b+X
=(m-1)x²+(2n+1)x+b
若代数式mX²+2nX-X²+b+X的值与字母X的取值无关,则所有含x项的系数为0,即 ：
m-1=0,且2n+1=0
m=1,n= -1/2
3m²-1/2n³-m²n+4n³+5 /2n³
=3m²-m²n+6n³
=3-(-1/2)+6(-1/2)³
=3+1/2-3/4
=3-1/4
=11/4