X2-13x-28=0

Solution for X2-13x-28=0 equation:

X2-13X-28=0

We add all the numbers together, and all the variables

X^2-13X-28=0

a = 1; b = -13; c = -28;
Δ = b2-4ac
Δ = -132-4·1·(-28)
Δ = 281
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{-(-13)-\sqrt{281}}{2*1}=\frac{13-\sqrt{281}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-13)+\sqrt{281}}{2*1}=\frac{13+\sqrt{281}}{2}
$