-290.25=300+2t-4.9t^2

Solution for -290.25=300+2t-4.9t^2 equation:

-290.25=300+2t-4.9t^2

We move all terms to the left:

-290.25-(300+2t-4.9t^2)=0

We get rid of parentheses

4.9t^2-2t-300-290.25=0

We add all the numbers together, and all the variables

4.9t^2-2t-590.25=0

a = 4.9; b = -2; c = -590.25;
Δ = b2-4ac
Δ = -22-4·4.9·(-590.25)
Δ = 11572.9
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-2)-\sqrt{11572.9}}{2*4.9}=\frac{2-\sqrt{11572.9}}{9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2)+\sqrt{11572.9}}{2*4.9}=\frac{2+\sqrt{11572.9}}{9.8}
$