-4.9t^2+21.76t-11=0

Solution for -4.9t^2+21.76t-11=0 equation:

-4.9t^2+21.76t-11=0

a = -4.9; b = 21.76; c = -11;
Δ = b2-4ac
Δ = 21.762-4·(-4.9)·(-11)
Δ = 257.8976
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{-(21.76)-\sqrt{257.8976}}{2*-4.9}=\frac{-21.76-\sqrt{257.8976}}{-9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21.76)+\sqrt{257.8976}}{2*-4.9}=\frac{-21.76+\sqrt{257.8976}}{-9.8}
$