-2n(3n+14)=-20

Solution for -2n(3n+14)=-20 equation:

-2n(3n+14)=-20

We move all terms to the left:

-2n(3n+14)-(-20)=0

We add all the numbers together, and all the variables

-2n(3n+14)+20=0

We multiply parentheses

-6n^2-28n+20=0

a = -6; b = -28; c = +20;
Δ = b2-4ac
Δ = -282-4·(-6)·20
Δ = 1264
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:

$\sqrt{\Delta}=\sqrt{1264}=\sqrt{16*79}=\sqrt{16}*\sqrt{79}=4\sqrt{79}$
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-28)-4\sqrt{79}}{2*-6}=\frac{28-4\sqrt{79}}{-12}
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-28)+4\sqrt{79}}{2*-6}=\frac{28+4\sqrt{79}}{-12}
$