已知9^m=3,9^n=4,则9^2m-n等于（ ）如题,请写出步骤.

已知3m=4n,则m/m+n+n/m-n-m^2/m^2-n^2= 已知m(m-3)-(m²-3n)=9,则(m²+n²)/2-mn=? 若(m-2n)/(2m+n)=3,则[3(m-2n)/(2m+n)-(m-2n)/[2(2m+n)] - {9(m-2n)/[4(2m+n)]}的值是? 已知m ,n均为正整数且满足(4m/3 )-75=n+(2m/9)则当m=（ ）时,n取得最小值（ ） 已知m.n.s为R+,m+n=2,m/s+n/t=9,s+t最小值是4/9则m和n分别为 已知m.n.s为R+,m+n=2,m/s+n/t=9,s+t最小值是4/9则m和n分别为 已知m^2+9n^2+6m+6n+10=0,求(m^2-6mn+9n^2)/(m-3n)-(4m^2-9n^2)/(2m-3n) 已知m^2+9n^+6m+6n+10=0,求(m^2-6mn+9n^2)÷(m-3n)-(4m^2-9n^2)÷(2m-3n)的值 已知4M+N=9,2M-3N=1,求(M+2N)²-（3M-N)²的值 已知4m+n=9,2m-3n=1,求(m+2n)²-(3m-n)²的值 已知2m-3n/3m+n=2,求4m-6n/9m+3n+18m+6n/4m-6n的值 已知2m-3n/3m+n=2 求(4m-6n/9m+3n)+(18m+6n/4m-6n)的值.要有步骤和讲解. 已知2m-3n/3m+n=2,求4m-6n/9m+3n+18m+6n/4m-6n的值 已知m-n=2 则3m^2-6mn+3n^2-9= 已知3^m=2,3^n=4,求9^m+1-2n 已知3^m=6,9^n=2,求3^(2m-4n+1) 已知3^M=6,9^N=2,求2^2M-4N+1 已知3m=2n,则m/(m+n)+n/(m-n)-n^2/(m^2-n^2)=?