5k2=2k+4

Solution for 5k2=2k+4 equation:

5k^2=2k+4

We move all terms to the left:

5k^2-(2k+4)=0

We get rid of parentheses

5k^2-2k-4=0

a = 5; b = -2; c = -4;
Δ = b2-4ac
Δ = -22-4·5·(-4)
Δ = 84
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:

$\sqrt{\Delta}=\sqrt{84}=\sqrt{4*21}=\sqrt{4}*\sqrt{21}=2\sqrt{21}$
$k_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-2)-2\sqrt{21}}{2*5}=\frac{2-2\sqrt{21}}{10}
$
$k_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2)+2\sqrt{21}}{2*5}=\frac{2+2\sqrt{21}}{10}
$