X2-15x-199.75=0

Solution for X2-15x-199.75=0 equation:

X2-15X-199.75=0

We add all the numbers together, and all the variables

X^2-15X-199.75=0

a = 1; b = -15; c = -199.75;
Δ = b2-4ac
Δ = -152-4·1·(-199.75)
Δ = 1024
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1024}=32$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-32}{2*1}=\frac{-17}{2}
=-8+1/2
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+32}{2*1}=\frac{47}{2}
=23+1/2
$