-280=56,6t-4,9t2

Solution for -280=56,6t-4,9t2 equation:

-280=56.6t-4.9t^2

We move all terms to the left:

-280-(56.6t-4.9t^2)=0

We get rid of parentheses

4.9t^2-56.6t-280=0

a = 4.9; b = -56.6; c = -280;
Δ = b2-4ac
Δ = -56.62-4·4.9·(-280)
Δ = 8691.56
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{-(-56.6)-\sqrt{8691.56}}{2*4.9}=\frac{56.6-\sqrt{8691.56}}{9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-56.6)+\sqrt{8691.56}}{2*4.9}=\frac{56.6+\sqrt{8691.56}}{9.8}
$