(7n+9)(4n-3)=0

Solution for (7n+9)(4n-3)=0 equation:

(7n+9)(4n-3)=0

We multiply parentheses ..

(+28n^2-21n+36n-27)=0

We get rid of parentheses

28n^2-21n+36n-27=0

We add all the numbers together, and all the variables

28n^2+15n-27=0

a = 28; b = 15; c = -27;
Δ = b2-4ac
Δ = 152-4·28·(-27)
Δ = 3249
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3249}=57$
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-57}{2*28}=\frac{-72}{56}
=-1+2/7
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+57}{2*28}=\frac{42}{56}
=3/4
$