CMR: a) 742³-692³ chia hết cho200 b) 685³+315³ chia hết cho 25 000

Question

CMR:
a) 742³-692³ chia hết cho200
b) 685³+315³ chia hết cho 25 000

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Calantha 4 years 2020-11-04T11:45:20+00:00 1 Answers 89 views 0

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  1. Adela
    0
    2020-11-04T11:46:56+00:00
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    Giải thích các bước giải:

     a) `742^3-692^3`

    `=(742-692)(742^2+742.692+692^2)`

    `=(742-692)(371^2 .2^2+2.371.2.346+346^2 .2^)`

    `=50.4(371^2+371.346+346^2)`

    `=200(371^2+371.346+346^2)vdots200`

     b) `685^3+315^3`

    `=(685+315)(685^2-685.315+315^2)`

    `=(685+315)(137^2 .5^2-5.137.5.63+63^2 .5^2)`

    `=1000.25(137^2-137.63+63^2)`

    `=25000(137^2-137.63+63^2)vdots25`

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Giải phương trình 1 ẩn: x + 2 - 2(x + 1) = -x . Hỏi x = ? ( )