x2-0.5x-39=0

Solution for x2-0.5x-39=0 equation:

x2-0.5x-39=0

We add all the numbers together, and all the variables

x^2-0.5x-39=0

a = 1; b = -0.5; c = -39;
Δ = b2-4ac
Δ = -0.52-4·1·(-39)
Δ = 156.25
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-0.5)-\sqrt{156.25}}{2*1}=\frac{0.5-\sqrt{156.25}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-0.5)+\sqrt{156.25}}{2*1}=\frac{0.5+\sqrt{156.25}}{2}
$