X2-4x-221=0

Solution for X2-4x-221=0 equation:

X2-4X-221=0

We add all the numbers together, and all the variables

X^2-4X-221=0

a = 1; b = -4; c = -221;
Δ = b2-4ac
Δ = -42-4·1·(-221)
Δ = 900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{900}=30$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-4)-30}{2*1}=\frac{-26}{2}
=-13
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+30}{2*1}=\frac{34}{2}
=17
$