已知,（-3a的n次方）的三次方与（2m-5）互为相反数,求（2分之m-2n）的n次方的值

【(-3a的n次方)的三次方,与(2m-5)a的九次方互为相反数,求二分之m-2n的n次方】
(-3a^n)^3+(2m-5)a^9 = 0
-27a^(3n) + (2m-5)a^9 = 0
27a^(3n) = (2m-5)a^9
27 = 2m-5,3n=9
m = 16,n = 3
[ (m-2n)/2 ] ^n = [ (16-2×3) /2 ]^3 = 5^3 = 125