t=-4.9t^2+12.5t+64.2

Solution for t=-4.9t^2+12.5t+64.2 equation:

t=-4.9t^2+12.5t+64.2

We move all terms to the left:

t-(-4.9t^2+12.5t+64.2)=0

We get rid of parentheses

4.9t^2-12.5t+t-64.2=0

We add all the numbers together, and all the variables

4.9t^2-11.5t-64.2=0

a = 4.9; b = -11.5; c = -64.2;
Δ = b2-4ac
Δ = -11.52-4·4.9·(-64.2)
Δ = 1390.57
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{-(-11.5)-\sqrt{1390.57}}{2*4.9}=\frac{11.5-\sqrt{1390.57}}{9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-11.5)+\sqrt{1390.57}}{2*4.9}=\frac{11.5+\sqrt{1390.57}}{9.8}
$