Factor completely: x² − 9 A (x − 3)² B (x + 3)² C (x − 3)(x + 3) D (x − 9)(x + 1) ✓ Correct Answer: Option C Difference of squares: a² − b² = (a−b)(a+b). x² − 9 = (x−3)(x+3). Practice ACT Exam Prep Quizzes → Browse All Questions Study Flashcards