0=70t^2+140t-70

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

0=70t^2+140t-70

We move all terms to the left:

0-(70t^2+140t-70)=0

We add all the numbers together, and all the variables

-(70t^2+140t-70)=0

We get rid of parentheses

-70t^2-140t+70=0

a = -70; b = -140; c = +70;
Δ = b2-4ac
Δ = -1402-4·(-70)·70
Δ = 39200
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:

$\sqrt{\Delta}=\sqrt{39200}=\sqrt{19600*2}=\sqrt{19600}*\sqrt{2}=140\sqrt{2}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-140)-140\sqrt{2}}{2*-70}=\frac{140-140\sqrt{2}}{-140}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-140)+140\sqrt{2}}{2*-70}=\frac{140+140\sqrt{2}}{-140}
$