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

Toán Lớp 8: hãy chứng tỏ (a-b+c) mũ 2=a mũ 2+bmũ2+cmũ2-2ab-2bc+2ca

Toán Lớp 8: hãy chứng tỏ
(a-b+c) mũ 2=a mũ 2+bmũ2+cmũ2-2ab-2bc+2ca

Comments ( 1 )

  1. (a-b+c)^2
    =(a-b+c)(a-b+c)
    =a(a-b+c)-b.(a-b+c)+c.(a-b+c)
    =a^2-ab+ac-(ab-b^2+bc)+ac-bc+c^2
    =a^2-ab+ac-ab+b^2-2bc+c^2
    =a^2+b^2+c^2-2ab-2bc+2ac
    =>(a-b+c)^2=a^2+b^2+c^2-2ab-2bc+2ac
    =>đpcm
    #Wuang
     

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

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