0=28x+4.9x^2

Solution for 0=28x+4.9x^2 equation:

0=28x+4.9x^2

We move all terms to the left:

0-(28x+4.9x^2)=0

We add all the numbers together, and all the variables

-(28x+4.9x^2)=0

We get rid of parentheses

-4.9x^2-28x=0

a = -4.9; b = -28; c = 0;
Δ = b2-4ac
Δ = -282-4·(-4.9)·0
Δ = 784
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{784}=28$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-28)-28}{2*-4.9}=\frac{0}{-9.8}
=0
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-28)+28}{2*-4.9}=\frac{56}{-9.8}
=-5+7/9.8
$