1≤lg(x/y)≤2
则
10≤x/y≤100
10y≤x≤100y
(100y)^(-5/9)≤x^(-5/9)≤(10y)^(-5/9).(1)
2≤lg（x^2/根号y）≤3
则
100根号y≤x^2≤1000根号y
(100根号y)^(16/9)≤(x^2)^(16/9)≤(1000根号y)^(16/9).(2)
(1)(2)两式相乘
10^(22/9)*y^(1/3)≤x^3≤10^(38/9)*y^(1/3)
10^(22/9)≤x^3/y^(1/3)≤10^(38/9)
22/9≤lg(x^3/y^(1/3))≤38/9