n(5n+8)=4

Solution for n(5n+8)=4 equation:

n(5n+8)=4

We move all terms to the left:

n(5n+8)-(4)=0

We multiply parentheses

5n^2+8n-4=0

a = 5; b = 8; c = -4;
Δ = b2-4ac
Δ = 82-4·5·(-4)
Δ = 144
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{144}=12$
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-12}{2*5}=\frac{-20}{10}
=-2
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+12}{2*5}=\frac{4}{10}
=2/5
$