Відповіді до вправ 401 - 500 » 445

Виконайте дії: 1) (7a + 9b)2 – (7a – 9b)2 = 49a2 + 126ab + 81b2 – (49a2 – –126ab + 81b2) = 49a2 + 126ab + 81b2 – 49a2 + 126ab – 81b2 = 252ab; 2) (10a – 3b)2 + (6a + 5b)2 = 100a2 – 60ab + 9b2 + 36a2 + 60ab + + 25b2 =136a2 + 34b2; 3) 18x2 – 12xy – 2(3x – у)2 = 18x2 – 12ху – 2(9х2 – 6ху + у2) = 18x2 – 12xу– 18x2 + 12ху – 2y2 = –2у2; 4) a(9a – 1)2 – 81a(a – 2)2 = a(81a2 – 18a + 1) – 81a(a2 – 4a + 4) = = 81a3 – 18a2 + a – 81a3 + 324a2 – 324a = 306a2 – 323a.