(15x+6)(x-1)=0

Solution for (15x+6)(x-1)=0 equation:

(15x+6)(x-1)=0

We multiply parentheses ..

(+15x^2-15x+6x-6)=0

We get rid of parentheses

15x^2-15x+6x-6=0

We add all the numbers together, and all the variables

15x^2-9x-6=0

a = 15; b = -9; c = -6;
Δ = b2-4ac
Δ = -92-4·15·(-6)
Δ = 441
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{441}=21$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9)-21}{2*15}=\frac{-12}{30}
=-2/5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9)+21}{2*15}=\frac{30}{30}
=1
$