0=-4.9t^2+39.2t+1.6

Solution for 0=-4.9t^2+39.2t+1.6 equation:

0=-4.9t^2+39.2t+1.6

We move all terms to the left:

0-(-4.9t^2+39.2t+1.6)=0

We add all the numbers together, and all the variables

-(-4.9t^2+39.2t+1.6)=0

We get rid of parentheses

4.9t^2-39.2t-1.6=0

a = 4.9; b = -39.2; c = -1.6;
Δ = b2-4ac
Δ = -39.22-4·4.9·(-1.6)
Δ = 1568
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{1568}=\sqrt{16*98}=\sqrt{16}*\sqrt{98}=4\sqrt{98}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-39.2)-4\sqrt{98}}{2*4.9}=\frac{39.2-4\sqrt{98}}{9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-39.2)+4\sqrt{98}}{2*4.9}=\frac{39.2+4\sqrt{98}}{9.8}
$