Question

How do you complete the square and solve `x^2+3x-28=0`?

Answer 1

`x =-7` and `x = 4`

Explanation:

First, to factor the quadratic equation we need to play with integers which multiple to 28: 1,28 and 2,14 and 4,7

Trying combinations of these allows us to rewrite this problem as:

`(x + 7)(x - 4) = 0`

We can now solve for `x + 7 = 0` and `x - 4 = 0`

`x + 7 = 0 -> x + 7 - 7 = 0 - 7 -> x =-7`

`x - 4 = 0 -> x -4 + 4 = 0 + 4 -> x = 4`