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

Toán Lớp 6: CMR: a(b+c)−b(a−c)=(a+b)c CMR: a(b−c)−a(b+d)=−a(c+d)

Toán Lớp 6: CMR: a(b+c)−b(a−c)=(a+b)c
CMR: a(b−c)−a(b+d)=−a(c+d)

Comments ( 2 )

  1. Giải đáp:
    Ta có :
    1)
    VT=a(b+c)-b(a-c)
    =a.b+a.c-b.a-b.(-c)
    =a.b+a.c-b.a+b.c
    =(a.b-b.a)+(a.c+b.c)
    =[a.(b-b)]+[c.(a+b)]
    =a.0+(a+b).c
    =0+(a+b).c
    =(a+b).c=VP  (đpcm)
    2)
    Ta có :
    VT=a(b-c)-a(b+d)=-a(c+d)
    =a.b-a.c-a.b-a.d
    =(a.b-a.b)-(a.c+a.d)
    =[a.(b-b)]-a.(c+d)
    =a.0-a.(c+d)
    =0-a.(c+d)
    =-a.(c+d)=VP   (Đpcm)

  2. Lời giải và giải thích chi tiết :
    a(b+c)-b(a-c)=ab+ac-ab+ab=ac+bc=(a+b)c
    a(b-c)-a(b+d)=ab-ac-ab-ad=-ac-ad=-a(c+d)

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