(0)=(5x-20)(6x+3)

Solution for (0)=(5x-20)(6x+3) equation:

(0)=(5x-20)(6x+3)

We move all terms to the left:

(0)-((5x-20)(6x+3))=0

We add all the numbers together, and all the variables

-((5x-20)(6x+3))=0

We multiply parentheses ..

-((+30x^2+15x-120x-60))=0


We calculate terms in parentheses: -((+30x^2+15x-120x-60)), so:

(+30x^2+15x-120x-60)

We get rid of parentheses

30x^2+15x-120x-60

We add all the numbers together, and all the variables

30x^2-105x-60

Back to the equation:

-(30x^2-105x-60)


We get rid of parentheses

-30x^2+105x+60=0

a = -30; b = 105; c = +60;
Δ = b2-4ac
Δ = 1052-4·(-30)·60
Δ = 18225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{18225}=135$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(105)-135}{2*-30}=\frac{-240}{-60}
=+4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(105)+135}{2*-30}=\frac{30}{-60}
=-1/2
$