0=1.25t^2-8.34t-8.34

Solution for 0=1.25t^2-8.34t-8.34 equation:

0=1.25t^2-8.34t-8.34

We move all terms to the left:

0-(1.25t^2-8.34t-8.34)=0

We add all the numbers together, and all the variables

-(1.25t^2-8.34t-8.34)=0

We get rid of parentheses

-1.25t^2+8.34t+8.34=0

a = -1.25; b = 8.34; c = +8.34;
Δ = b2-4ac
Δ = 8.342-4·(-1.25)·8.34
Δ = 111.2556
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{-(8.34)-\sqrt{111.2556}}{2*-1.25}=\frac{-8.34-\sqrt{111.2556}}{-2.5}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8.34)+\sqrt{111.2556}}{2*-1.25}=\frac{-8.34+\sqrt{111.2556}}{-2.5}
$