7by+4b-14y-8,если y=5/28 ,b=2/7

Если y = 5/28,b = 2/7 то 7by + 4b - 14y - 8 = 7 * 2/7 * 5/28 + 4 * 2/7 - 14 * 5/28 - 8 = (7 * 2 * 5)/(7 * 28) + (4 * 2)/7 - (14 * 5)/28 - 8 = (1 * 1 * 5)/(1 * 14) + (4 * 2)/7 - (1 * 5)/2 - 8 = 5/14 + 8/7 - 5/2 - 8 = 5/14 + 1 1/7 - 2 1/2 - 8 = 5/14 + 1 2/14 - 2 7/14 - 8 = 1 7/14 - 2 7/14 - 8 = - 1 - 8 = -9. Ответ: -9.