Question

Which of the following is a solution of (x - 5)(x + 7) = 3x + 21
0
45
8
5

Answer 1

`(x - 5)(x + 7) = 3 x + 21`

`(x - 5)(x + 7) = 3(x + 7)`

`(x - 5)(x + 7) - 3(x + 7) = 0 \\`

`(x + 7)(x - 5 - 3) = 0`

`(x + 7)(x - 8) = 0`

`x + 7 = 0 \\ x = - 7`

Or

`x - 8 = 0 \\ x = 8`