Tính: A = 2019 nhân 20182018 trừ 2018 nhân 20192019
Giải thích
A = 2019.20182018 – 2018.20192019
= 2019.(20180000+2018) – 2018.(20190000+2019)
= 2019.2018.104 + 2019.2018 – 2018.2019.104 – 2018.2019
= (2019.2018.104 – 2018.2019.104) + (2019.2018 – 2018.2019)
= 0 + 0 = 0