156=-13t^2+104t

Solution for 156=-13t^2+104t equation:

156=-13t^2+104t

We move all terms to the left:

156-(-13t^2+104t)=0

We get rid of parentheses

13t^2-104t+156=0

a = 13; b = -104; c = +156;
Δ = b2-4ac
Δ = -1042-4·13·156
Δ = 2704
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2704}=52$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-104)-52}{2*13}=\frac{52}{26}
=2
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-104)+52}{2*13}=\frac{156}{26}
=6
$