20=4.9*t^2

Solution for 20=4.9*t^2 equation:

Simplifying
20 = 4.9t2

Solving
20 = 4.9t2

Solving for variable 't'.

Move all terms containing t to the left, all other terms to the right.

Add '-4.9t2' to each side of the equation.
20 + -4.9t2 = 4.9t2 + -4.9t2

Combine like terms: 4.9t2 + -4.9t2 = 0.0
20 + -4.9t2 = 0.0

Add '-20' to each side of the equation.
20 + -20 + -4.9t2 = 0.0 + -20

Combine like terms: 20 + -20 = 0
0 + -4.9t2 = 0.0 + -20
-4.9t2 = 0.0 + -20

Combine like terms: 0.0 + -20 = -20
-4.9t2 = -20

Divide each side by '-4.9'.
t2 = 4.081632653

Simplifying
t2 = 4.081632653

Take the square root of each side:
t = {-2.020305089, 2.020305089}