25.714=-12t+4.9t^2

Solution for 25.714=-12t+4.9t^2 equation:

25.714=-12t+4.9t^2

We move all terms to the left:

25.714-(-12t+4.9t^2)=0

We get rid of parentheses

-4.9t^2+12t+25.714=0

a = -4.9; b = 12; c = +25.714;
Δ = b2-4ac
Δ = 122-4·(-4.9)·25.714
Δ = 647.9944
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{-(12)-\sqrt{647.9944}}{2*-4.9}=\frac{-12-\sqrt{647.9944}}{-9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+\sqrt{647.9944}}{2*-4.9}=\frac{-12+\sqrt{647.9944}}{-9.8}
$