0=-0.1t^2+0.9

Solution for 0=-0.1t^2+0.9 equation:

Simplifying
0 = -0.1t2 + 0.9

Reorder the terms:
0 = 0.9 + -0.1t2

Solving
0 = 0.9 + -0.1t2

Solving for variable 't'.

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

Add '0.1t2' to each side of the equation.
0 + 0.1t2 = 0.9 + -0.1t2 + 0.1t2
Remove the zero:
0.1t2 = 0.9 + -0.1t2 + 0.1t2

Combine like terms: -0.1t2 + 0.1t2 = 0.0
0.1t2 = 0.9 + 0.0
0.1t2 = 0.9

Divide each side by '0.1'.
t2 = 9

Simplifying
t2 = 9

Take the square root of each side:
t = {-3, 3}