8^m=2^3m=3
9^n=3^2n=2
6^(3m)*3^(m+2n)
=2^(3m)*3^(3m)*3^(m+2n)
=2^(3m)*3^(4m+2n)
=2^(3m)*3^(4m)*3^(2n)
=6*3^(4m)
算不出具体值