a , 7 . ( x -2 ) – 5 ( x – 4) = 28 b , ( x – 3 )² – 48 = -12 c , -7 – 2x = -37 – ( -26 )

`\text{a)}`

`7(x – 2) – 5(x – 4) = 28`

`7(x – 2) = 28 + 5(x – 4)`

`7x – 14 = 28 + 5x – 20`

`7x – 5x = 28 – 20 + 14`

`2x = 22`

`x = 11`

`\text{b)}`

`(x – 3)^2 – 48 = -12`

`(x – 3)^2 = -12 + 48`

`(x – 3)^2 = 36`

`(x – 3)^2 = 6^2`

`⇒ x -3 = 6 → x = 9` `\text{hoặc}` `x -3 = -6 ⇒ x = -3` 

`\text{c)}`

`-7 -2x = -37 – (-26)`

`-7 – 2x = -11`

` 2x = -7 +11`

`2x = 4`

`x = 2`