x2-15x-126=0

Solution for x2-15x-126=0 equation:

x2-15x-126=0

We add all the numbers together, and all the variables

x^2-15x-126=0

a = 1; b = -15; c = -126;
Δ = b2-4ac
Δ = -152-4·1·(-126)
Δ = 729
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{729}=27$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-27}{2*1}=\frac{-12}{2}
=-6
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+27}{2*1}=\frac{42}{2}
=21
$