Bài 8)
d. Ta có: $8^{5}$ = $8^{5}$
⇒ $8^{5}$ < 3. $4^{7}$ . $8^{5}$
Vậy $8^{5}$ < 3. $4^{7}$ . $8^{5}$
Bài 11)
A = $\frac{2^{30} . 5^7 + 2^{13} . 5^{27}}{2^{27}.5^7+2^{10}.5^{27}}$
A = $\frac{2^{13}.5^7(2^{17} + 5^{20})}{2^{10}.5^7(2^{17} + 5^{20})}$
A = $\frac{2^{13}.5^7}{2^{10}.5^7}$
A = $\frac{2^3}{1}$
A = $\frac{8}{1}$
A = 8
Vậy A = 8