x2-4x-6.25=0

Solution for x2-4x-6.25=0 equation:

x2-4x-6.25=0

We add all the numbers together, and all the variables

x^2-4x-6.25=0

a = 1; b = -4; c = -6.25;
Δ = b2-4ac
Δ = -42-4·1·(-6.25)
Δ = 41
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{-(-4)-\sqrt{41}}{2*1}=\frac{4-\sqrt{41}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+\sqrt{41}}{2*1}=\frac{4+\sqrt{41}}{2}
$