r^2-22+21=0

Solution for r^2-22+21=0 equation:

Simplifying
r2 + -22 + 21 = 0

Reorder the terms:
-22 + 21 + r2 = 0

Combine like terms: -22 + 21 = -1
-1 + r2 = 0

Solving
-1 + r2 = 0

Solving for variable 'r'.

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

Add '1' to each side of the equation.
-1 + 1 + r2 = 0 + 1

Combine like terms: -1 + 1 = 0
0 + r2 = 0 + 1
r2 = 0 + 1

Combine like terms: 0 + 1 = 1
r2 = 1

Simplifying
r2 = 1

Take the square root of each side:
r = {-1, 1}