0=-4.9x^2+31x

Solution for 0=-4.9x^2+31x equation:

0=-4.9x^2+31x

We move all terms to the left:

0-(-4.9x^2+31x)=0

We add all the numbers together, and all the variables

-(-4.9x^2+31x)=0

We get rid of parentheses

4.9x^2-31x=0

a = 4.9; b = -31; c = 0;
Δ = b2-4ac
Δ = -312-4·4.9·0
Δ = 961
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{961}=31$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-31)-31}{2*4.9}=\frac{0}{9.8}
=0
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-31)+31}{2*4.9}=\frac{62}{9.8}
=6+1/3.0625
$