найти D (f) если f(x) =корень из -5/х^2 +3х - х-1/х+1

advantages: 1. You can study longer than others, who wants to sleep2. You can read a lot of books3. You don't waste your time to sleepingdisadvantages: 1. You always feel tired2. It can badly affect on your health3. You will have a patient view