(7x+3)(4x-3)=0

Solution for (7x+3)(4x-3)=0 equation:

(7x+3)(4x-3)=0

We multiply parentheses ..

(+28x^2-21x+12x-9)=0

We get rid of parentheses

28x^2-21x+12x-9=0

We add all the numbers together, and all the variables

28x^2-9x-9=0

a = 28; b = -9; c = -9;
Δ = b2-4ac
Δ = -92-4·28·(-9)
Δ = 1089
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1089}=33$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9)-33}{2*28}=\frac{-24}{56}
=-3/7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9)+33}{2*28}=\frac{42}{56}
=3/4
$