0=-4.9t^2+27.5t+8.7

Solution for 0=-4.9t^2+27.5t+8.7 equation:

0=-4.9t^2+27.5t+8.7

We move all terms to the left:

0-(-4.9t^2+27.5t+8.7)=0

We add all the numbers together, and all the variables

-(-4.9t^2+27.5t+8.7)=0

We get rid of parentheses

4.9t^2-27.5t-8.7=0

a = 4.9; b = -27.5; c = -8.7;
Δ = b2-4ac
Δ = -27.52-4·4.9·(-8.7)
Δ = 926.77
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{-(-27.5)-\sqrt{926.77}}{2*4.9}=\frac{27.5-\sqrt{926.77}}{9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-27.5)+\sqrt{926.77}}{2*4.9}=\frac{27.5+\sqrt{926.77}}{9.8}
$