(a+b+c)^2+(a+b-c)^2 -4c^2 mong mn giúp đỡ :<

Question

(a+b+c)^2+(a+b-c)^2 -4c^2
mong mn giúp đỡ :<

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Dulcie 5 years 2020-10-24T16:57:53+00:00 2 Answers 137 views 0

Answers ( )

  1. Helga
    0
    2020-10-24T16:59:01+00:00
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    Đáp án:

    Ta có : 

    `(a + b + c)^2 + (a + b – c)^2 – 4c^2`

    `=  (a + b + c)^2 + [(a + b – c)^2 – (2c)^2]`

    `= (a + b + c)^2 + (a + b – c – 2c)(a + b – c + 2c)`

    `= (a + b + c)^2 + (a + b – 3c)(a + b + c)`

    `= (a + b + c)(a + b + c + a + b – 3c)`

    `= (a + b + c)(2a + 2b – 2c)`

    `= 2(a + b + c)(a + b – c)`

    Giải thích các bước giải:

     

  2. Nho
    0
    2020-10-24T16:59:30+00:00
    Reply

    `(a+b+c)^2+(a+b-c)^2-4c^2`

    `=a^2+b^2+c^2+2ab+2bc+2ac+a^2+b^2+c^2 +2ab-2ac-2bc-4c^2`

    `=2a^2+2b^2-2c^2+4ab`

    `=2(a^2+b^2+2ab-c^2)`

    `=2.[(a+b)^2-c^2]`

    `=2(a+b+c)(a+b-c)`

     

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