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

Toán Lớp 8: Chứng minh giúp em vs ạ [(a+b)+c]²=a²+b²+c²+2ab+2cb+2ac [(a+b)-c]²=a²+b²+c²+2ab-2cb-2ac

Toán Lớp 8: Chứng minh giúp em vs ạ
[(a+b)+c]²=a²+b²+c²+2ab+2cb+2ac
[(a+b)-c]²=a²+b²+c²+2ab-2cb-2ac

Comments ( 1 )

  1. Các bước giải:
    a/[(a+b)+c]²=a²+b²+c²+2ab+2cb+2ac
     VT=[(a+b)+c]²
    =(a+b)²+2ac+2bc+c²
    =a²+2ab+b²+2ac+2bc+c²
    =a²+b²+c²+2ab+2cb+2ac=VP(đpcm)
    b/[(a+b)-c]²=a²+b²+c²+2ab-2cb-2ac
    VT=[(a+b)-c]²
    =(a+b)²-2ac-2bc+c²
    =a²+2ab+b²-2ac-2bc+c²
    =a²+b²+c²+2ab-2cb-2ac=VP(đpcm)

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