Help ugenttt!!Am nevoie de ajutor
Tot exercitiul 2 va rog!!

2019² - 2019·2020 =
= 2019(2019 - 2020)
= 2019·(-1)
= - 2019
2019² - 2018·2019 =
= 2019(2019 - 2018)
= 2019·(1)
= 2019
5 + 10 + 15 + .. + 2020 - 5·(1 + 2 + 3 + .. + 404)
= 5·(1 + 2 + 3 + .. + 404) - 5·(1 + 2 + 3 + .. + 404)
= 0