Question

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

Answer 1

`x=(-b+-sqrt(b^2-4ac))/(2a)`
is the quadratic formula where:
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;
`ax^2 + bx +c=0` . Do this by moving the 9 to the left side
you then get the equation:
`x^2+4x-9=0`
As stated above, you know the values of a, b and c.
Simply sub these into the quadratic formula.
`x=(-4+-sqrt((4)^2-4xx1xx(-9)))/(2xx1)`

hope it helps

Answer 2

`1.606, -5.606`

Explanation:

Rearrange the formula to equal zero
`x^2+4x-9=0`

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

Substitute into the quadratic equation.
`x=(-b+- sqrt(b^2-4ac))/(2a)`

`x=(-4+- sqrt(4^2-4*1*-9))/(2*1)`

`x=(-4+- sqrt(52))/2`

`x=(-4+7.2111)/2` and `(-4-7.2111)/2`