因为4^m = a ,8^n = b
① 2的2m+3n次方
=2^2m*2^3n
=4^m*8^n
=ab
② 2的4m-6n次方
=2^4m/2^6n
=(2^2)^2n/(2^3)^2n
=4^2n/8^2n
=(4^n)^2/(8^n)^2
=a²/b²