2. Prove that there is no integer 𝑛 such that 7|4𝑛^2βˆ’3

3. Find the remainder by division by 7 of 99999999.
4. Find the remainder in the division by 17 of 15!
5. Let 𝑝 be a prime. Show that for all integerπ‘Žπ‘Ž we have that 𝑝|π‘Žπ‘+(π‘βˆ’1)!π‘Ž and 𝑝|π‘Ž+(π‘βˆ’1)!π‘Žπ‘.