70t^2+140t-40=0

Solution for 70t^2+140t-40=0 equation:

70t^2+140t-40=0

a = 70; b = 140; c = -40;
Δ = b2-4ac
Δ = 1402-4·70·(-40)
Δ = 30800
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{30800}=\sqrt{400*77}=\sqrt{400}*\sqrt{77}=20\sqrt{77}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(140)-20\sqrt{77}}{2*70}=\frac{-140-20\sqrt{77}}{140}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(140)+20\sqrt{77}}{2*70}=\frac{-140+20\sqrt{77}}{140}
$