9.8t^2+2t-20=0

Solution for 9.8t^2+2t-20=0 equation:

9.8t^2+2t-20=0

a = 9.8; b = 2; c = -20;
Δ = b2-4ac
Δ = 22-4·9.8·(-20)
Δ = 788
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:

$\sqrt{\Delta}=\sqrt{788}=\sqrt{4*197}=\sqrt{4}*\sqrt{197}=2\sqrt{197}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(2)-2\sqrt{197}}{2*9.8}=\frac{-2-2\sqrt{197}}{19.6}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(2)+2\sqrt{197}}{2*9.8}=\frac{-2+2\sqrt{197}}{19.6}
$