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

Nov 28, 2016

$x = - 7$ 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:

$\left(x + 7\right) \left(x - 4\right) = 0$

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

$x + 7 = 0 \to x + 7 - 7 = 0 - 7 \to x = - 7$

$x - 4 = 0 \to x - 4 + 4 = 0 + 4 \to x = 4$