2(x+5)(x-8)=0

Solution for 2(x+5)(x-8)=0 equation:

2(x+5)(x-8)=0

We multiply parentheses ..

2(+x^2-8x+5x-40)=0

We multiply parentheses

2x^2-16x+10x-80=0

We add all the numbers together, and all the variables

2x^2-6x-80=0

a = 2; b = -6; c = -80;
Δ = b2-4ac
Δ = -62-4·2·(-80)
Δ = 676
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{676}=26$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-6)-26}{2*2}=\frac{-20}{4}
=-5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-6)+26}{2*2}=\frac{32}{4}
=8
$