28x-4.9x^2=13

Solution for 28x-4.9x^2=13 equation:

28x-4.9x^2=13

We move all terms to the left:

28x-4.9x^2-(13)=0

a = -4.9; b = 28; c = -13;
Δ = b2-4ac
Δ = 282-4·(-4.9)·(-13)
Δ = 529.2
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{529.2}}{2*-4.9}=\frac{-28-\sqrt{529.2}}{-9.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(28)+\sqrt{529.2}}{2*-4.9}=\frac{-28+\sqrt{529.2}}{-9.8}
$