5n2-4n-10=15

Solution for 5n2-4n-10=15 equation:

5n^2-4n-10=15

We move all terms to the left:

5n^2-4n-10-(15)=0

We add all the numbers together, and all the variables

5n^2-4n-25=0

a = 5; b = -4; c = -25;
Δ = b2-4ac
Δ = -42-4·5·(-25)
Δ = 516
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{516}=\sqrt{4*129}=\sqrt{4}*\sqrt{129}=2\sqrt{129}$
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-4)-2\sqrt{129}}{2*5}=\frac{4-2\sqrt{129}}{10}
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+2\sqrt{129}}{2*5}=\frac{4+2\sqrt{129}}{10}
$