36=28x-4.9x^2

Solution for 36=28x-4.9x^2 equation:

36=28x-4.9x^2

We move all terms to the left:

36-(28x-4.9x^2)=0

We get rid of parentheses

4.9x^2-28x+36=0

a = 4.9; b = -28; c = +36;
Δ = b2-4ac
Δ = -282-4·4.9·36
Δ = 78.4
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{-(-28)-\sqrt{78.4}}{2*4.9}=\frac{28-\sqrt{78.4}}{9.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-28)+\sqrt{78.4}}{2*4.9}=\frac{28+\sqrt{78.4}}{9.8}
$