-11=5x-4.905x^2

Solution for -11=5x-4.905x^2 equation:

-11=5x-4.905x^2

We move all terms to the left:

-11-(5x-4.905x^2)=0

We get rid of parentheses

4.905x^2-5x-11=0

a = 4.905; b = -5; c = -11;
Δ = b2-4ac
Δ = -52-4·4.905·(-11)
Δ = 240.82
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{-(-5)-\sqrt{240.82}}{2*4.905}=\frac{5-\sqrt{240.82}}{9.81}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+\sqrt{240.82}}{2*4.905}=\frac{5+\sqrt{240.82}}{9.81}
$