0=7x^2-12x-4

Solution for 0=7x^2-12x-4 equation:

0=7x^2-12x-4

We move all terms to the left:

0-(7x^2-12x-4)=0

We add all the numbers together, and all the variables

-(7x^2-12x-4)=0

We get rid of parentheses

-7x^2+12x+4=0

a = -7; b = 12; c = +4;
Δ = b2-4ac
Δ = 122-4·(-7)·4
Δ = 256
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{256}=16$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-16}{2*-7}=\frac{-28}{-14}
=+2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+16}{2*-7}=\frac{4}{-14}
=-2/7
$