X2+15x-800=0

Solution for X2+15x-800=0 equation:

X2+15X-800=0

We add all the numbers together, and all the variables

X^2+15X-800=0

a = 1; b = 15; c = -800;
Δ = b2-4ac
Δ = 152-4·1·(-800)
Δ = 3425
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{3425}=\sqrt{25*137}=\sqrt{25}*\sqrt{137}=5\sqrt{137}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-5\sqrt{137}}{2*1}=\frac{-15-5\sqrt{137}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+5\sqrt{137}}{2*1}=\frac{-15+5\sqrt{137}}{2}
$