(14s+9)(5s-15)=0

Solution for (14s+9)(5s-15)=0 equation:

(14s+9)(5s-15)=0

We multiply parentheses ..

(+70s^2-210s+45s-135)=0

We get rid of parentheses

70s^2-210s+45s-135=0

We add all the numbers together, and all the variables

70s^2-165s-135=0

a = 70; b = -165; c = -135;
Δ = b2-4ac
Δ = -1652-4·70·(-135)
Δ = 65025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$s_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$s_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{65025}=255$
$s_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-165)-255}{2*70}=\frac{-90}{140}
=-9/14
$
$s_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-165)+255}{2*70}=\frac{420}{140}
=3
$