(7x-9)(2x+8)=0

Solution for (7x-9)(2x+8)=0 equation:

(7x-9)(2x+8)=0

We multiply parentheses ..

(+14x^2+56x-18x-72)=0

We get rid of parentheses

14x^2+56x-18x-72=0

We add all the numbers together, and all the variables

14x^2+38x-72=0

a = 14; b = 38; c = -72;
Δ = b2-4ac
Δ = 382-4·14·(-72)
Δ = 5476
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{5476}=74$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(38)-74}{2*14}=\frac{-112}{28}
=-4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(38)+74}{2*14}=\frac{36}{28}
=1+2/7
$