(4x+15)(x+1)=0

Solution for (4x+15)(x+1)=0 equation:

(4x+15)(x+1)=0

We multiply parentheses ..

(+4x^2+4x+15x+15)=0

We get rid of parentheses

4x^2+4x+15x+15=0

We add all the numbers together, and all the variables

4x^2+19x+15=0

a = 4; b = 19; c = +15;
Δ = b2-4ac
Δ = 192-4·4·15
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{-(19)-11}{2*4}=\frac{-30}{8}
=-3+3/4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(19)+11}{2*4}=\frac{-8}{8}
=-1
$