20k2-81k=40

Solution for 20k2-81k=40 equation:

20k^2-81k=40

We move all terms to the left:

20k^2-81k-(40)=0

a = 20; b = -81; c = -40;
Δ = b2-4ac
Δ = -812-4·20·(-40)
Δ = 9761
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$k_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$k_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$k_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-81)-\sqrt{9761}}{2*20}=\frac{81-\sqrt{9761}}{40}
$
$k_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-81)+\sqrt{9761}}{2*20}=\frac{81+\sqrt{9761}}{40}
$