(7x+9)(8x-3)=0

Solution for (7x+9)(8x-3)=0 equation:

(7x+9)(8x-3)=0

We multiply parentheses ..

(+56x^2-21x+72x-27)=0

We get rid of parentheses

56x^2-21x+72x-27=0

We add all the numbers together, and all the variables

56x^2+51x-27=0

a = 56; b = 51; c = -27;
Δ = b2-4ac
Δ = 512-4·56·(-27)
Δ = 8649
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{8649}=93$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(51)-93}{2*56}=\frac{-144}{112}
=-1+2/7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(51)+93}{2*56}=\frac{42}{112}
=3/8
$