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

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

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

We multiply parentheses ..

(+56x^2+49x-72x-63)=0

We get rid of parentheses

56x^2+49x-72x-63=0

We add all the numbers together, and all the variables

56x^2-23x-63=0

a = 56; b = -23; c = -63;
Δ = b2-4ac
Δ = -232-4·56·(-63)
Δ = 14641
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{14641}=121$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-23)-121}{2*56}=\frac{-98}{112}
=-7/8
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-23)+121}{2*56}=\frac{144}{112}
=1+2/7
$