a² + 2ab + b² + 4a + 4b + 4 = (a² + 2ab + b)² + (4a + 4b) + 4 =
= (a + b)² + 4(a + b) + 4 = (a + b)² + 2 * 2 * (a + b) + 2² = (a + b + 2)² =
= (a + b + 2)(a + b + 2)
