§ 6. Множення і ділення раціональних чисел » 1228

Спростіть вираз: 1) –7(а – 2b + 2) – 2(5а – 5) = –7a + 14b – 14 – 10a + 10 = 14b – 17a – 4; 2) a(3x – 2y + 5) – 2a(–2x – y) = 3ax – 2ay + 5a + 4ax + 2ay = 7ax + 5a; 3) 21/3a – 11/6a – 5/9a = 22/6a – 11/6a – 5/9a = 7/6a – 5/9a = 21/18a – 10/18a = 11/18a; 4) –21/4x + 1,6x – 5/8x = –2,25x + 1,6x – 0,625x = –1,275x; 5) –(33/4b – 2/9) + 4(11/8b – 1/6) = –15/4b + 2/9 + 4 • 9/8b – 4 • 1/6 = –15/4b + 2/9 + 9/2b – 2/3 = –15/4b + 2/9 + 18/4b – 6/9 = 3/4b – 4/9; 6) 2 • (13/8x – 3/4y) – (31/2x – 2y) = 2 • 11/8x – 2 • 3/4y – 7/2x + 2y = 11/4x – 3/2y – 7/2x + 2y = 11/4x – 3/2y – 14/4x + 4/2y = –3/4x + 1/2y.