0=4.9t^2-10t-70

Solution for 0=4.9t^2-10t-70 equation:

0=4.9t^2-10t-70

We move all terms to the left:

0-(4.9t^2-10t-70)=0

We add all the numbers together, and all the variables

-(4.9t^2-10t-70)=0

We get rid of parentheses

-4.9t^2+10t+70=0

a = -4.9; b = 10; c = +70;
Δ = b2-4ac
Δ = 102-4·(-4.9)·70
Δ = 1472
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:

$\sqrt{\Delta}=\sqrt{1472}=\sqrt{64*23}=\sqrt{64}*\sqrt{23}=8\sqrt{23}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(10)-8\sqrt{23}}{2*-4.9}=\frac{-10-8\sqrt{23}}{-9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(10)+8\sqrt{23}}{2*-4.9}=\frac{-10+8\sqrt{23}}{-9.8}
$