Найдите значение выражения (1/5a+1/7a)a2/4 при a = 7,7.

(1/5* a + 1/7 * a) * a * 2/4, при a = 7,7.

(1/5 * 7,7 + 1/7 * 7,7) * 7,7 * 2/4 = 10,164. 

1) 1/5 * 7,7 = 1/5 * 7 7/10 = 1/5 * 77/10 = (1 * 77) / (5 * 10) = 77/50 = 1 27/50;

2) 1/7 * 7,7 = 1/7 * 7 7/10 = 1/7 * 77/10 = (1 * 77) / (7 * 10) = 77/70 = 1 7/70 = 1 1/10;

3) 1 27/50 + 1 1/10 = 77/50 + 11/10 = 77/50 + (11 * 5) / (10 * 5) = 77/50 + 55/50 = 132/50 = 2 32/50 = 2 16/25; 

4) 2 16/25 * 7,7 = 66/25 * 7 7/10 = 66/25 * 77/10 = (66 * 77) / (25 * 10) = 5082/250 = 20 82/250 = 20 41/125; 

5) 20 41/125 * 2/4 = 2541/125 * 2/4 = 5082/500 = 10,164.