Вправи 801- 887 » 819

819. Обчисли. а) (4√12 – 6√48 + 5√27) √3 – 12 = 4√36 – 6√144 + 5√81 – 12 = 24 – 72 + 45 – 12 = –15. б) (2√320 – 7√20 – √45)2 + 20 = (2 • 8√5 – 7 • 2√5 – 3√5)2 + 20 = (16√5 – 14√5 – 3√5)2 + 20 = (–√5)2 + 20 = 25; в) (√28 + √63) : √7 = (2√7+ 3√7)/√7 = 5; г) (3√28+ 2√175)/(2√112) = (6√7+ 10√7)/(4√7) = (16√7)/(4√7) = 4.