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

Toán Lớp 8: Hãy chứng minh đẳng thức sau: a. (????+????)^2−(????+????)(????−????)=2(????+????) b. ????^2+????^2=(????−????)^2+2???????? c. ????^2+????^2=(????+????)^2−2????????

Tháng Chín 20, 2022 Toán học 1 Comment 0 views

Toán Lớp 8: Hãy chứng minh đẳng thức sau:
a. (????+????)^2−(????+????)(????−????)=2(????+????)
b. ????^2+????^2=(????−????)^2+2????????
c. ????^2+????^2=(????+????)^2−2????????

Comments ( 1 )

  1. dananhnhu2k4
    dananhnhu2k4
    20 Tháng Chín, 2022 at 9:55 sáng
    Reply
    a) $(a+b)^2-(a+b)(a-b)$
    $=a^2+2ab+b^2-(a^2-b^2)$
    $=(a^2-a^2)+(b^2+b^2)+2ab$
    $=2b^2+2ab$
    $=2b(a+b)$ (đpcm)
    b) $(x-y)^2+2xy$
    $=x^2-2xy+y^2+2xy$
    $=x^2+y^2$ (đpcm)
    c) $(x+y)^2-2xy$
    $=x^2+2xy+y^2-2xy$
    $=x^2+y^2$ (đpcm)
     

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

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