0=-4.9t2+25t+80

Solution for 0=-4.9t2+25t+80 equation:

0=-4.9t^2+25t+80

We move all terms to the left:

0-(-4.9t^2+25t+80)=0

We add all the numbers together, and all the variables

-(-4.9t^2+25t+80)=0

We get rid of parentheses

4.9t^2-25t-80=0

a = 4.9; b = -25; c = -80;
Δ = b2-4ac
Δ = -252-4·4.9·(-80)
Δ = 2193
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{-(-25)-\sqrt{2193}}{2*4.9}=\frac{25-\sqrt{2193}}{9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-25)+\sqrt{2193}}{2*4.9}=\frac{25+\sqrt{2193}}{9.8}
$