a) 115 + 5 ( x – 4 ) = 120 b) 5|x| – 10^0 = 3^7 : 3^5 c) 2^2016 . 2^x-1 = 2^2015

* Hướng dẫn giải

a) 115 + 5 ( x – 4 ) = 120

5 ( x – 4 ) = 120 – 115

5 ( x – 4 ) = 5

x – 4 = 5 : 5

x – 4 = 1

x = 1 + 4

x = 5

b)  5|x| – ${10}^0=3^7:3^5$

5| x | – 1 = $3^2$

5| x | = 9 + 1

5| x | = 10

| x | = 2

x = 2 hoặc x = -2

c) $2^{2016}.2^{x-1}=2^{2015}$

$2^{x-1}=2^{2015}: 2^{2016}$

$2^{x-1}=2^{2015-2016}$

$2^{x-1}=2^{-1}$

⇒ x – 1 = -1

x = -1 + 1

x = 0