-9x-15=-2x(x+4)

Solution for -9x-15=-2x(x+4) equation:

-9x-15=-2x(x+4)

We move all terms to the left:

-9x-15-(-2x(x+4))=0


We calculate terms in parentheses: -(-2x(x+4)), so:

-2x(x+4)

We multiply parentheses

-2x^2-8x

Back to the equation:

-(-2x^2-8x)


We get rid of parentheses

2x^2+8x-9x-15=0

We add all the numbers together, and all the variables

2x^2-1x-15=0

a = 2; b = -1; c = -15;
Δ = b2-4ac
Δ = -12-4·2·(-15)
Δ = 121
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{121}=11$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-1)-11}{2*2}=\frac{-10}{4}
=-2+1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1)+11}{2*2}=\frac{12}{4}
=3
$