a) 4x² + 12x + 9 = (2x + 3)² = (2x + 3)(2x + 3)
б) 25b² + 10b + 1 = (5b + 1)² = (5b + 1)(5b + 1)
Ответ: (2x + 3)(2x + 3), (5b + 1)(5b + 1)