x^2-70x+400=0

Solution for x^2-70x+400=0 equation:

x^2-70x+400=0

a = 1; b = -70; c = +400;
Δ = b2-4ac
Δ = -702-4·1·400
Δ = 3300
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:

$\sqrt{\Delta}=\sqrt{3300}=\sqrt{100*33}=\sqrt{100}*\sqrt{33}=10\sqrt{33}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-70)-10\sqrt{33}}{2*1}=\frac{70-10\sqrt{33}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-70)+10\sqrt{33}}{2*1}=\frac{70+10\sqrt{33}}{2}
$