2^x=4^5.4^3 2^x=4^5.16^2 2^x=4^7/4^3 (-5)^x=25/-5

Đáp án:

1/ $2^{x} = 4^{5} . 4^{3}$

     $2^{x} = 4^{5+3}$

     $2^{x} = 4^{8}$

     $2^{x} = (2²)^{8}$

     $2^{x} = 2^{16}$

     Vậy $x = 16$

2/ $2^{x} = 4^{5} . 16^{2}$

$2^{x} = 4^{5} . (4²)²$

$2^{x} = 4^{5} . 4^{4}$

$2^{x} = 4^{5+4}$

$2^{x} = 4^{9}$

$2^{x} = (2²)^{9}$

$2^{x} = (2)^{18}$

Vậy $x = 18$

3/ $2^{x} = \dfrac{4^{7}}{4^{3}}$

$2^{x} = 4^{7} : 4^{3}$

$2^{x} = 4^{7-3}$

$2^{x} = 4^{4}$

$2^{x} = (2²)^{4}$

$2^{x} = (2)^{8}$

Vậy $x = 8$

4/ $(-5)^{x} = \dfrac{25}{-5}$

$(-5)^{x} = 25 : (-5)$

$(-5)^{x} = -5$

$(-5)^{x} = -5^{1}$

Vậy $x = 1$