F5=27x-4.9x^2

Solution for F5=27x-4.9x^2 equation:

5=27F-4.9F^2

We move all terms to the left:

5-(27F-4.9F^2)=0

We get rid of parentheses

4.9F^2-27F+5=0

a = 4.9; b = -27; c = +5;
Δ = b2-4ac
Δ = -272-4·4.9·5
Δ = 631
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$F_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$F_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-27)-\sqrt{631}}{2*4.9}=\frac{27-\sqrt{631}}{9.8}
$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-27)+\sqrt{631}}{2*4.9}=\frac{27+\sqrt{631}}{9.8}
$