Вычислите: а) 1/3*(3/5*5/7)+1/3*(5/9*9/7); б) 7/3*6/17+1/8:17/6:

Вычислим значения выражений:

а) 1/3 * (3/5 * 5/7) + 1/3 * (5/9 * 9/7) = 1/3 * 3/5 * 5/7 + 1/3 * 5/9 * 9/7 = 1/1 * 1/5 * 5/7 + 1/3 * 5/1 * 1/7 = 1/5 * 5/7 + 5/3 * 1/7 = 1/7 + 1/7 * 5/3 = 1/7 * (1 + 5/3) = 1/7 * (3/3 + 5/3) = 1/7 * 8/3 = 8/(7 * 3) = 8/21; 

б) 7/3 * 6/17 + 1/8 : 17/6 = 7/3 * 6/7 + 1/8 * 6/17 = 1/3 * 6/1 + 1/4 * 3/17 = 2 + 3/68 = (2 * 68 + 3)/68 = 139/68.