2.5=13x-4.9x^2

Solution for 2.5=13x-4.9x^2 equation:

2.5=13x-4.9x^2

We move all terms to the left:

2.5-(13x-4.9x^2)=0

We get rid of parentheses

4.9x^2-13x+2.5=0

a = 4.9; b = -13; c = +2.5;
Δ = b2-4ac
Δ = -132-4·4.9·2.5
Δ = 120
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{120}=\sqrt{4*30}=\sqrt{4}*\sqrt{30}=2\sqrt{30}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-13)-2\sqrt{30}}{2*4.9}=\frac{13-2\sqrt{30}}{9.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-13)+2\sqrt{30}}{2*4.9}=\frac{13+2\sqrt{30}}{9.8}
$