5^m=2,5^n =4
25 ^(2m-n)+125^ (m+n)
=5^2(2m-n)+5^3(m+n)
=5^4m/5^2n+5^3m*5^3n
=(5^m)^4/(5^n)^2+(5^m)^3*(5^n)^3
=2^4/4^2+2^3*4^3
=16/16+8*64
=1+512=513