200-2x-4.9x^2=0

Solution for 200-2x-4.9x^2=0 equation:

200-2x-4.9x^2=0

a = -4.9; b = -2; c = +200;
Δ = b2-4ac
Δ = -22-4·(-4.9)·200
Δ = 3924
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:

$\sqrt{\Delta}=\sqrt{3924}=\sqrt{4*981}=\sqrt{4}*\sqrt{981}=2\sqrt{981}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-2)-2\sqrt{981}}{2*-4.9}=\frac{2-2\sqrt{981}}{-9.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2)+2\sqrt{981}}{2*-4.9}=\frac{2+2\sqrt{981}}{-9.8}
$