400=-16t^2+4000

Solution for 400=-16t^2+4000 equation:

Simplifying
400 = -16t2 + 4000

Reorder the terms:
400 = 4000 + -16t2

Solving
400 = 4000 + -16t2

Solving for variable 't'.

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

Add '16t2' to each side of the equation.
400 + 16t2 = 4000 + -16t2 + 16t2

Combine like terms: -16t2 + 16t2 = 0
400 + 16t2 = 4000 + 0
400 + 16t2 = 4000

Add '-400' to each side of the equation.
400 + -400 + 16t2 = 4000 + -400

Combine like terms: 400 + -400 = 0
0 + 16t2 = 4000 + -400
16t2 = 4000 + -400

Combine like terms: 4000 + -400 = 3600
16t2 = 3600

Divide each side by '16'.
t2 = 225

Simplifying
t2 = 225

Take the square root of each side:
t = {-15, 15}