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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 6: So sánh `2021^70 – 2021^69` và `2021^69 – 2021^68`

Toán Lớp 6: So sánh
2021^70 – 2021^69 và 2021^69 – 2021^68

Comments ( 2 )

  1. Answer
    $\text{Ta có:}$
    2021^70 – 2021^69
    = 2021^69 . (2021 – 1)
    = 2021^69 . 2020
    $\text{Ta có:}$
    2021^69 – 2021^68
    = 2021^68 . (2021 – 1)
    = 2021^68 . 2020
    $\text{Vì}$ 2021^69 > 2021^68 $\text{nên}$ 2021^69 . 2020 > 2021^68 . 2020
    => 2021^70 – 2021^69 > 2021^69 – 2021^68
    $\text{Vậy}$ 2021^70 – 2021^69 > 2021^69 – 2021^68

  2. Ta có :
    2021^70 – 2021^69 = 2021^69 . ( 2021 – 1 )
                                     = 2021^69 . 2020
    2021^69 – 2021^68 = 2021^68 . ( 2021 – 1 )
                                     = 2021^68 . 2020
    Vì 2021^69 . 2020 > 2021^68 . 2020
    ⇒ 2021^70 – 2021^69 > 2021^69 – 2021^68

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222-9+11+12:2*14+14 = ? ( )