23.9. г) (c² - cd + d²)(c - d).

Recognize the difference of cubes formula: a³ - b³ = (a - b)(a² + ab + b²).

1. The given expression is (c² - cd + d²)(c - d). This matches the formula with a = c and b = d.
2. Therefore, (c² - cd + d²)(c - d) = c³ - d³.

Answer: c³ - d³