4/sqrt(7) + 1/2sqrt(7) + 3/5sqrt(7) + 4/10sqrt(7) =
= 4sqrt(7)/7 + 2sqrt(7)/28 + 15sqrt(7)/175 + 40sqrt(7)/700 =
= 4sqrt(7)/7 + sqrt(7)/14 + 3sqrt(7)/35 + 4sqrt(7)/70 =
= 40sqrt(7)/70 + 5sqrt(7)/70 + 6sqrt(7)/70 + 4sqrt(7)/70 =
= 60sqrt(7)/70 =
= 6sqrt(7)/7 =
= 6/sqrt(7)
sqrt(x) = radical din x, in caz ca nu stii