X2-28x+140=0

Solution for X2-28x+140=0 equation:

X2-28X+140=0

We add all the numbers together, and all the variables

X^2-28X+140=0

a = 1; b = -28; c = +140;
Δ = b2-4ac
Δ = -282-4·1·140
Δ = 224
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:

$\sqrt{\Delta}=\sqrt{224}=\sqrt{16*14}=\sqrt{16}*\sqrt{14}=4\sqrt{14}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-28)-4\sqrt{14}}{2*1}=\frac{28-4\sqrt{14}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-28)+4\sqrt{14}}{2*1}=\frac{28+4\sqrt{14}}{2}
$