-5r^2+20=0

Solution for -5r^2+20=0 equation:

Simplifying
-5r2 + 20 = 0

Reorder the terms:
20 + -5r2 = 0

Solving
20 + -5r2 = 0

Solving for variable 'r'.

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

Add '-20' to each side of the equation.
20 + -20 + -5r2 = 0 + -20

Combine like terms: 20 + -20 = 0
0 + -5r2 = 0 + -20
-5r2 = 0 + -20

Combine like terms: 0 + -20 = -20
-5r2 = -20

Divide each side by '-5'.
r2 = 4

Simplifying
r2 = 4

Take the square root of each side:
r = {-2, 2}