0=-4.9t^2+30t+0.8

Solution for 0=-4.9t^2+30t+0.8 equation:

0=-4.9t^2+30t+0.8

We move all terms to the left:

0-(-4.9t^2+30t+0.8)=0

We add all the numbers together, and all the variables

-(-4.9t^2+30t+0.8)=0

We get rid of parentheses

4.9t^2-30t-0.8=0

a = 4.9; b = -30; c = -0.8;
Δ = b2-4ac
Δ = -302-4·4.9·(-0.8)
Δ = 915.68
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{-(-30)-\sqrt{915.68}}{2*4.9}=\frac{30-\sqrt{915.68}}{9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-30)+\sqrt{915.68}}{2*4.9}=\frac{30+\sqrt{915.68}}{9.8}
$