ВН Валерий Н (a-3b): 3 = (3b-a):4, 4*(a-3b) = 3*(3b-a), 4a - 12b = 9b - 3a, 7a = 21b, a = 3b, (a^2 - b^2)/(a*b) = (9*b^2 - b^2)/(3*b^2) = 8/3.