Bạn xem hình câu $1;2;3;4;5;6$
Câu $13$.
$2S_{1} = S^{2}$ ($A$ đúng)
$S_{2} - S_{1} = 2 + 2^2 + 2^3 +2^4 + ...... + 2^{64} + 2^{65} - 1 - 2 - 2^2 - 2^3 - ........ - 2^{64}$
$= 2^{65} - 1$ ($B;C$ đúng)
$⇒$ $D$ sai vì : $S_{2} - S_{1} = S_{1}$
$→$ Chọn $D$
Câu $14$.
$A = \dfrac{4^{16} . 4^{10} - 2^{32} . 4^8}{16^8 . 4^8} = \dfrac{2^{32} . 2^{20} - 2^{32} . 2^{16}}{2^{32} . 2^{16}} = \dfrac{2^{32} . 2^{16} . (2^{4} - 1)}{2^{32} . 2^{16}} = 2^4 -1 = 16 - 1 = 15$
$→$ Chọn $D$
Câu $15$.
$B = \dfrac{8^{10} + 4^{10}}{8^4 + 4^{11}} : 4^4 = \dfrac{2^{30} + 2^{20}}{2^{12} + 2^{22}} : 4^4 = \dfrac{2^{20} . (2^{10} + 1)}{2^{12} . ( 1 + 2^{10})} : 4^4 = 2^8 : 2^8 = 1$
$→$ Chọn $A$
