0=50.625+8x-4.9x^2

Solution for 0=50.625+8x-4.9x^2 equation:

0=50.625+8x-4.9x^2

We move all terms to the left:

0-(50.625+8x-4.9x^2)=0

We add all the numbers together, and all the variables

-(50.625+8x-4.9x^2)=0

We get rid of parentheses

4.9x^2-8x-50.625=0

a = 4.9; b = -8; c = -50.625;
Δ = b2-4ac
Δ = -82-4·4.9·(-50.625)
Δ = 1056.25
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-8)-\sqrt{1056.25}}{2*4.9}=\frac{8-\sqrt{1056.25}}{9.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8)+\sqrt{1056.25}}{2*4.9}=\frac{8+\sqrt{1056.25}}{9.8}
$