10^(3m-n)=10^3m/10^n=2^3/3=8/3
y=27^m-a=3^3m-a=x^3-a
x=2^m-1 ==> 2^m=x+1
y=3+4^m=3+2^2m=3+(x+1)^2=x^2+2x+4