(5n+3)(4n+5)=0

Solution for (5n+3)(4n+5)=0 equation:

(5n+3)(4n+5)=0

We multiply parentheses ..

(+20n^2+25n+12n+15)=0

We get rid of parentheses

20n^2+25n+12n+15=0

We add all the numbers together, and all the variables

20n^2+37n+15=0

a = 20; b = 37; c = +15;
Δ = b2-4ac
Δ = 372-4·20·15
Δ = 169
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{169}=13$
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(37)-13}{2*20}=\frac{-50}{40}
=-1+1/4
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(37)+13}{2*20}=\frac{-24}{40}
=-3/5
$