(14c-8)(5c+9)=0

Solution for (14c-8)(5c+9)=0 equation:

(14c-8)(5c+9)=0

We multiply parentheses ..

(+70c^2+126c-40c-72)=0

We get rid of parentheses

70c^2+126c-40c-72=0

We add all the numbers together, and all the variables

70c^2+86c-72=0

a = 70; b = 86; c = -72;
Δ = b2-4ac
Δ = 862-4·70·(-72)
Δ = 27556
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{27556}=166$
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(86)-166}{2*70}=\frac{-252}{140}
=-1+4/5
$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(86)+166}{2*70}=\frac{80}{140}
=4/7
$