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

Toán Lớp 8: Thu gọn biểu thức : (a-b)^3+(a+b)^3-6ab^2

Toán Lớp 8: Thu gọn biểu thức : (a-b)^3+(a+b)^3-6ab^2

Comments ( 2 )

  1. (a-b)^3+(a+b)^3 – 6ab^2
    = a^3-3a^2b + 3ab^2 -b^3 + a^3+3a^2b+3ab^2+b^3-6ab^2
    = (a^3+a^3)-(3a^2b-3a^2b)+(b^3-b^3)+(3ab^2+3ab^2-6ab^2)
    = 2a^3 – 0 + 0 + 0
    =2a^3
    #wcdi
     

  2. $ (a-b)^3+(a+b)^3-6ab^2$
    $=(a^3-3a^2b+3ab^2-b^3)+(a^3+3a^2b+3ab^2+b^3)-6ab^2$
    $=a^3-3a^2b+3ab^2-b^3+a^3+3a^2b+3ab^2+b^3-6ab^2$
    $=2a^3-3a^2b+3ab^2+3a^2b+3ab^2-6ab^2$
    $=2a^3+6ab^2-6ab^2$
    $=2a^3$

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