(5x+30)(x-3)=0

Solution for (5x+30)(x-3)=0 equation:

(5x+30)(x-3)=0

We multiply parentheses ..

(+5x^2-15x+30x-90)=0

We get rid of parentheses

5x^2-15x+30x-90=0

We add all the numbers together, and all the variables

5x^2+15x-90=0

a = 5; b = 15; c = -90;
Δ = b2-4ac
Δ = 152-4·5·(-90)
Δ = 2025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2025}=45$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-45}{2*5}=\frac{-60}{10}
=-6
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+45}{2*5}=\frac{30}{10}
=3
$