0=7x^2-20x-3

Solution for 0=7x^2-20x-3 equation:

0=7x^2-20x-3

We move all terms to the left:

0-(7x^2-20x-3)=0

We add all the numbers together, and all the variables

-(7x^2-20x-3)=0

We get rid of parentheses

-7x^2+20x+3=0

a = -7; b = 20; c = +3;
Δ = b2-4ac
Δ = 202-4·(-7)·3
Δ = 484
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{484}=22$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-22}{2*-7}=\frac{-42}{-14}
=+3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+22}{2*-7}=\frac{2}{-14}
=-1/7
$