9k2+4k-80=0

Solution for 9k2+4k-80=0 equation:

9k^2+4k-80=0

a = 9; b = 4; c = -80;
Δ = b2-4ac
Δ = 42-4·9·(-80)
Δ = 2896
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$k_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$k_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{2896}=\sqrt{16*181}=\sqrt{16}*\sqrt{181}=4\sqrt{181}$
$k_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(4)-4\sqrt{181}}{2*9}=\frac{-4-4\sqrt{181}}{18}
$
$k_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4)+4\sqrt{181}}{2*9}=\frac{-4+4\sqrt{181}}{18}
$