100+26x-0,05x^2=0

Solution for 100+26x-0,05x^2=0 equation:

100+26x-0.05x^2=0

a = -0.05; b = 26; c = +100;
Δ = b2-4ac
Δ = 262-4·(-0.05)·100
Δ = 696
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:

$\sqrt{\Delta}=\sqrt{696}=\sqrt{4*174}=\sqrt{4}*\sqrt{174}=2\sqrt{174}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(26)-2\sqrt{174}}{2*-0.05}=\frac{-26-2\sqrt{174}}{-0.1}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(26)+2\sqrt{174}}{2*-0.05}=\frac{-26+2\sqrt{174}}{-0.1}
$