Y=-4.9x^2+18.9x+2.8

Solution for Y=-4.9x^2+18.9x+2.8 equation:

=-4.9Y^2+18.9Y+2.8

We move all terms to the left:

-(-4.9Y^2+18.9Y+2.8)=0

We get rid of parentheses

4.9Y^2-18.9Y-2.8=0

a = 4.9; b = -18.9; c = -2.8;
Δ = b2-4ac
Δ = -18.92-4·4.9·(-2.8)
Δ = 412.09
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-18.9)-\sqrt{412.09}}{2*4.9}=\frac{18.9-\sqrt{412.09}}{9.8}
$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-18.9)+\sqrt{412.09}}{2*4.9}=\frac{18.9+\sqrt{412.09}}{9.8}
$