-4.9t^2+22.5t+4=0

Solution for -4.9t^2+22.5t+4=0 equation:

-4.9t^2+22.5t+4=0

a = -4.9; b = 22.5; c = +4;
Δ = b2-4ac
Δ = 22.52-4·(-4.9)·4
Δ = 584.65
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{-(22.5)-\sqrt{584.65}}{2*-4.9}=\frac{-22.5-\sqrt{584.65}}{-9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(22.5)+\sqrt{584.65}}{2*-4.9}=\frac{-22.5+\sqrt{584.65}}{-9.8}
$