0=4.9t^2-11t-81

Solution for 0=4.9t^2-11t-81 equation:

0=4.9t^2-11t-81

We move all terms to the left:

0-(4.9t^2-11t-81)=0

We add all the numbers together, and all the variables

-(4.9t^2-11t-81)=0

We get rid of parentheses

-4.9t^2+11t+81=0

a = -4.9; b = 11; c = +81;
Δ = b2-4ac
Δ = 112-4·(-4.9)·81
Δ = 1708.6
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{-(11)-\sqrt{1708.6}}{2*-4.9}=\frac{-11-\sqrt{1708.6}}{-9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(11)+\sqrt{1708.6}}{2*-4.9}=\frac{-11+\sqrt{1708.6}}{-9.8}
$