1=3.9*t^2

Solution for 1=3.9*t^2 equation:

Simplifying
1 = 3.9t2

Solving
1 = 3.9t2

Solving for variable 't'.

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

Add '-3.9t2' to each side of the equation.
1 + -3.9t2 = 3.9t2 + -3.9t2

Combine like terms: 3.9t2 + -3.9t2 = 0.0
1 + -3.9t2 = 0.0

Add '-1' to each side of the equation.
1 + -1 + -3.9t2 = 0.0 + -1

Combine like terms: 1 + -1 = 0
0 + -3.9t2 = 0.0 + -1
-3.9t2 = 0.0 + -1

Combine like terms: 0.0 + -1 = -1
-3.9t2 = -1

Divide each side by '-3.9'.
t2 = 0.2564102564

Simplifying
t2 = 0.2564102564

Take the square root of each side:
t = {-0.506369684, 0.506369684}