3) (3a + 4)² – (a – 12)² = (3a + 4 – a + 12)(3a + 4 + a – 12) = (2a + 16)(4a – 8);
4) (5x – 7)² – (5 – 3x)² = (5x – 7 – 5 + 3x)(5x – 7 + 5 – 3x) = (8x – 12)(2x – 2);
5) (a² + 6ab + 16b²)² – (6ab + 20b²)² =
(a² + 6ab + 16b² – 6ab – 20b²)(a² + 6ab + 16b² + 6ab + 20b²) =
(a² – 4b²)(a² + 12ab + 36b²) =
(a² – (2b)²)(a + 6b)² =
(a – 2b)(a + 2b)(a + 6b)(a + 6b);
6) (4 – 6y³ + 4y⁶)² – (6y³ – 5y⁶)² =
(4 – 6y³ + 4y⁶ – 6y³ + 5y⁶)(4 – 6y³ + 4y⁶ + 6y³ – 5y⁶) =
(4 – 12y³ + 9y⁶)(4 – y⁶) =
(2² – 12y³ + (3y³)²)(2² – (y³)²) =
(2 – 3y)²(2 – y³)(2 + y³) =
(2 – 3y)(2 – 3y)(2 – y³)(2 + y³)