Разбираемся:
Давай сначала упростим исходное выражение:
3 ⋅ (1/(6a) − 1/(7b)) : (b/6 − a/7) = 3 ⋅ ((7b - 6a) / (42ab)) : ((7b - 6a) / 42) = 3 ⋅ ((7b - 6a) / (42ab)) ⋅ (42 / (7b - 6a)) = 3 ⋅ (1 / (ab))
Теперь подставим значения a = √18 и b = 1/√2:
a = √18 = √(9 ⋅ 2) = 3√2 b = 1/√2
Тогда ab = (3√2) ⋅ (1/√2) = 3
И, наконец, 3 ⋅ (1 / (ab)) = 3 ⋅ (1/3) = 1
Ответ: 1