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(a – 4)² – a(a + b) = a² – 8a + 16 – a² – ab = –8a – ab + 16

(y – 5 – 5y)(y – 2) = (–5 – 4y)(y – 2) = –5y + 10 – 4y² + 8y = –4y² + 3y + 10

(2x – 3y)² + (3x + 2y)² = 4x² – 12xy + 9y² + 9x² + 12xy + 4y² = 13x² + 13y²

(5a + 3b)² – (5a – 3b)² = 25a² + 30ab + 9b² – 25a² + 30ab – 9b² = 60ab