5n^2+15=28n

Solution for 5n^2+15=28n equation:

5n^2+15=28n

We move all terms to the left:

5n^2+15-(28n)=0

a = 5; b = -28; c = +15;
Δ = b2-4ac
Δ = -282-4·5·15
Δ = 484
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{484}=22$
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-28)-22}{2*5}=\frac{6}{10}
=3/5
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-28)+22}{2*5}=\frac{50}{10}
=5
$