a đề sai
b) 75^20 = ( 5*5*3)^20= 5^40 * 3^20 = 5^30 * ( 5^10 * 9^10)= 5^30 * 45^10.
\(12^8.12^{16}=12^{24}=\left(2^2.3\right)^{24}=2^{48}.3^{24}=2^{32}.2^{16}.3^{24}\)
\(4^{16}.3^{40}=\left(2^2\right)^{16}.3^{40}=2^{32}.3^{40}=2^{32}.3^{24}.3^{16}\)
\(12^8.12^{16}\ne4^{16}.3^{40}\)
\(75^{20}=\left(3.5^2\right)^{20}=3^{20}.5^{40}\)
\(45^{10}.5^{30}=\left(3^2.5\right)^{10}.5^{30}=3^{20}.5^{40}\)
\(75^{20}=45^{10}.5^{30}\)