Bài 2 :Tìm x biếttttttt

$\text{Đáp án + Giái thích các bước giải}$ 

$\\$ `m) 3^x + 3^(x+3) = 756`

$\\$ `=> 3^x + 3^x. 3^3 = 756`

$\\$ `=> 3^x .( 1 + 27) = 756`

$\\$ `=> 3^x . 28 = 756`

$\\$ `=> 3^x = 756 : 28`

$\\$` => 3^x = 27`

$\\$ `=> 3^x = 3^3`

$\\$` => x =3`

$\\$ Vậy : `x = 3` 

$\\$ `n) 5^(x+1) + 6. 5^(x+1) = 875`

$\\$` => 5^(x+1) . (1 + 6) = 875`

$\\$ `=> 5^(x+1) . 7 = 875`

$\\$` => 5^(x+1) = 875 : 7`

$\\$ `=> 5^(x+1) = 125`

$\\$` => 5^(x+1) = 125`

$\\$` => 5^(x+1) = 5^3`

$\\$ `=> x +1 = 3`

$\\$ `=> x = 2`

$\\$ Vậy : `x =2`