0=-4.9t^2+15t+381

Solution for 0=-4.9t^2+15t+381 equation:

0=-4.9t^2+15t+381

We move all terms to the left:

0-(-4.9t^2+15t+381)=0

We add all the numbers together, and all the variables

-(-4.9t^2+15t+381)=0

We get rid of parentheses

4.9t^2-15t-381=0

a = 4.9; b = -15; c = -381;
Δ = b2-4ac
Δ = -152-4·4.9·(-381)
Δ = 7692.6
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{-(-15)-\sqrt{7692.6}}{2*4.9}=\frac{15-\sqrt{7692.6}}{9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+\sqrt{7692.6}}{2*4.9}=\frac{15+\sqrt{7692.6}}{9.8}
$