t^2-13.9t-13.9=0

Solution for t^2-13.9t-13.9=0 equation:

t^2-13.9t-13.9=0

a = 1; b = -13.9; c = -13.9;
Δ = b2-4ac
Δ = -13.92-4·1·(-13.9)
Δ = 248.81
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{-(-13.9)-\sqrt{248.81}}{2*1}=\frac{13.9-\sqrt{248.81}}{2}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-13.9)+\sqrt{248.81}}{2*1}=\frac{13.9+\sqrt{248.81}}{2}
$