5t+4.9t^2-800=0

Solution for 5t+4.9t^2-800=0 equation:

5t+4.9t^2-800=0

a = 4.9; b = 5; c = -800;
Δ = b2-4ac
Δ = 52-4·4.9·(-800)
Δ = 15705
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:

$\sqrt{\Delta}=\sqrt{15705}=\sqrt{1*15705}=\sqrt{1}*\sqrt{15705}=1\sqrt{15705}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(5)-1\sqrt{15705}}{2*4.9}=\frac{-5-1\sqrt{15705}}{9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(5)+1\sqrt{15705}}{2*4.9}=\frac{-5+1\sqrt{15705}}{9.8}
$