Tính A = 1 + 2 – 3 – 4 + 5 + 6 – 7 – 8 + 9 + ... + 2018 – 2019 – 2020 + 2021 – 2022 + 2023.
Giải thích
A = 1 + 2 – 3 – 4 + 5 + 6 – 7 – 8 + 9 + ... + 2018 – 2019 – 2020 + 2021 – 2022 + 2023
A = (1 + 2 – 3 – 4) + (5 + 6 – 7 – 8) + … + (2017 + 2018 – 2019 – 2020) + 2021 – 2022 + 2023
A = (–4) + (–4) + … + (–4) + 2021 – 2022 + 2023
A = (–4) . 505 + 2021 + 1
A = (–2020) + 2021 + 1
A = 2.
Vậy A = 2.