(5x-7)(x+7)=0

Solution for (5x-7)(x+7)=0 equation:

(5x-7)(x+7)=0

We multiply parentheses ..

(+5x^2+35x-7x-49)=0

We get rid of parentheses

5x^2+35x-7x-49=0

We add all the numbers together, and all the variables

5x^2+28x-49=0

a = 5; b = 28; c = -49;
Δ = b2-4ac
Δ = 282-4·5·(-49)
Δ = 1764
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1764}=42$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(28)-42}{2*5}=\frac{-70}{10}
=-7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(28)+42}{2*5}=\frac{14}{10}
=1+2/5
$