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

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

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

We move all terms to the left:

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

We get rid of parentheses

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

We add all the numbers together, and all the variables

4.9t^2-27.5t=0

a = 4.9; b = -27.5; c = 0;
Δ = b2-4ac
Δ = -27.52-4·4.9·0
Δ = 756.25
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{756.25}}{2*4.9}=\frac{27.5-\sqrt{756.25}}{9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-27.5)+\sqrt{756.25}}{2*4.9}=\frac{27.5+\sqrt{756.25}}{9.8}
$