# How do you solve x^2+4x=9 using the quadratic formula?

Mar 13, 2018

$x = \frac{- b \pm \sqrt{{b}^{2} - 4 a c}}{2 a}$
a=number in front of x^2 (which is 1)
b= number in front of x (a coefficient, which is 4
c= the constant (which is -9)

#### Explanation:

First, you want to make sure the equation is in the form;
$a {x}^{2} + b x + c = 0$ . Do this by moving the 9 to the left side
you then get the equation:
${x}^{2} + 4 x - 9 = 0$
As stated above, you know the values of a, b and c.
Simply sub these into the quadratic formula.
$x = \frac{- 4 \pm \sqrt{{\left(4\right)}^{2} - 4 \times 1 \times \left(- 9\right)}}{2 \times 1}$

hope it helps

Mar 13, 2018

$1.606 , - 5.606$

#### Explanation:

Rearrange the formula to equal zero
${x}^{2} + 4 x - 9 = 0$

The coefficients of the expression are:
a=1, b=4, c=-9

$x = \frac{- b \pm \sqrt{{b}^{2} - 4 a c}}{2 a}$
$x = \frac{- 4 \pm \sqrt{{4}^{2} - 4 \cdot 1 \cdot - 9}}{2 \cdot 1}$
$x = \frac{- 4 \pm \sqrt{52}}{2}$
$x = \frac{- 4 + 7.2111}{2}$ and $\frac{- 4 - 7.2111}{2}$