-20a^2+405=0

Solution for -20a^2+405=0 equation:

Simplifying
-20a2 + 405 = 0

Reorder the terms:
405 + -20a2 = 0

Solving
405 + -20a2 = 0

Solving for variable 'a'.

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

Add '-405' to each side of the equation.
405 + -405 + -20a2 = 0 + -405

Combine like terms: 405 + -405 = 0
0 + -20a2 = 0 + -405
-20a2 = 0 + -405

Combine like terms: 0 + -405 = -405
-20a2 = -405

Divide each side by '-20'.
a2 = 20.25

Simplifying
a2 = 20.25

Take the square root of each side:
a = {-4.5, 4.5}