287. Упростите: a) (-0,7x + 0,6y) 5-3 (0,4y – 1,5x); б) 2/9 (1,8-1 1/2 a)-1 1/6 (1,2-2/7 a).

a) (-0,7x + 0,6y) * 5 - 3 * (0,4y - 1,5x) = -3,5x + 3y - 1,2y + 4,5x = (-3,5 + 4,5)x + (3 - 1,2)y = 1x + 1,8y = x + 1,8y б) 2/9 * (1,8 - 1 1/2 a) - 1 1/6 * (1,2 - 2/7 a) = 2/9 * (18/10 - 3/2 a) - 7/6 * (12/10 - 2/7 a) = 36/90 - 6/18 a - 84/60 + 14/42 a = 2/5 - 1/3 a - 14/10 + 1/3 a = 2/5 - 7/5 = -5/5 = -1 Ответ: a) x + 1,8y; б) -1