a)2x + 3x + 5x = 2 mũ : 5 mũ 2 b) 4x mũ 3 + 15 = 47 c) 4 . 2 mũ x – 3 = 125

`2x + 3x + 5x = 2^2 : 5^2`

`=> 10x = 0,16`

`=> x = 0,16 : 10`

`=> x = 0,016`

Vậy `x = 0,016`

`4x^3 + 15 = 47`

`=> 4x^3 = 47 – 15`

`=> 4x^3 = 32`

`=> x^3 = 32 : 4`

`=> x^3 = 8`

`=> x^3 = 2^3`

`=> x = 2`

Vậy `x = 2`

`4 . 2^x – 3 = 125`

`=> 4 . 2^x = 125 + 3`

`=> 4 . 2^x = 128`

`=> 2^x = 128 : 4`

`=> 2^x = 32`

`=> 2^x = 2^5`

`=> x = 5`

Vậy `x = 5`