Упростите 2^2х * 5^х + 20^х - 2^(х+1) * 10^х

2^2х * 5^х + 20^х - 2^(х+1) * 10^х = (2^2)^х * 5^х + 20^х - 2^х * 2^1 * 10^х = 4^х * 5^х + 20^х - 2^х * 2 * 10^х = 20^х + 20^х - 2*20^х = 20^х * (1+1-2) = 20^х * 0 = 0