22. (x² - 16)² + (x² + x - 12)² = 0

For the sum of squares to be zero, each term must be zero.

x² - 16 = 0 => x = ±4

x² + x - 12 = 0 => (x+4)(x-3) = 0 => x = -4 or x = 3

The common solution is x = -4.