X2-21x-270=0

Solution for X2-21x-270=0 equation:

X2-21X-270=0

We add all the numbers together, and all the variables

X^2-21X-270=0

a = 1; b = -21; c = -270;
Δ = b2-4ac
Δ = -212-4·1·(-270)
Δ = 1521
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1521}=39$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-21)-39}{2*1}=\frac{-18}{2}
=-9
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-21)+39}{2*1}=\frac{60}{2}
=30
$