4.9t^2-100t-100=0

Solution for 4.9t^2-100t-100=0 equation:

4.9t^2-100t-100=0

a = 4.9; b = -100; c = -100;
Δ = b2-4ac
Δ = -1002-4·4.9·(-100)
Δ = 11960
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:

$\sqrt{\Delta}=\sqrt{11960}=\sqrt{4*2990}=\sqrt{4}*\sqrt{2990}=2\sqrt{2990}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-100)-2\sqrt{2990}}{2*4.9}=\frac{100-2\sqrt{2990}}{9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-100)+2\sqrt{2990}}{2*4.9}=\frac{100+2\sqrt{2990}}{9.8}
$