400=f^2

Solution for 400=f^2 equation:

Simplifying
400 = f2

Solving
400 = f2

Solving for variable 'f'.

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

Add '-1f2' to each side of the equation.
400 + -1f2 = f2 + -1f2

Combine like terms: f2 + -1f2 = 0
400 + -1f2 = 0

Add '-400' to each side of the equation.
400 + -400 + -1f2 = 0 + -400

Combine like terms: 400 + -400 = 0
0 + -1f2 = 0 + -400
-1f2 = 0 + -400

Combine like terms: 0 + -400 = -400
-1f2 = -400

Divide each side by '-1'.
f2 = 400

Simplifying
f2 = 400

Take the square root of each side:
f = {-20, 20}