(2^41 + 4^20)/(8^13 + 4^20) =
= [2^41 + (2^2)^20]/[(2^3)^13 + (2^2)^20] =
= (2^41 + 2^40)/(2^39 + 2^40) =
= 2^40(2 + 1)/2^39(1 + 2) =
= (2^40×3)/(2^39×3) =
= 2
