Tính nhanh:2020.2020-2018.2022

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1. $2020.2020-2018.2022$

   $=2020.2020-(2020-2).(2020+2)$

   $=2020.2020-[2020.(2020+2)-2(2020+2)]$

   $=2020^2-[2020^2+4040-4040-4]$

   $=2020^2-[2020^2-4]$

   $=2020^2-2020^2+4$

   $=2^2=4$

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2. 2020 . 2020 – 2018 . 2022

   = 2020 . 2020 – 2018 . (2020 + 2)

   = 2020 . 2020 – (2018 . 2020 + 2018 + 2018)

   = 2020 . 2020 – (2018 . 2020 + 2020 – 2 + 2020 – 2)

   = 2020 . 2020 – ((2018 + 2) . 2020 – 2 – 2)

   = 2020 . 2020 – 2020 . 2020 – 4

   = 0 – 4

   = -4

   Chúc học tốt!!!

    

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