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

Toán Lớp 8: B = ab(a+b) – bc(b+c) + ca(a-c) C = ab(a+b) + bc(b+c) + ca(c+a)

Toán Lớp 8: B = ab(a+b) – bc(b+c) + ca(a-c)
C = ab(a+b) + bc(b+c) + ca(c+a)

Comments ( 2 )

  1. Giải đáp:
    B=(a+b)(b+c)(a-c)
    C=(a+b+c)(ab+bc+ac)
    Lời giải và giải thích chi tiết:
    B=ab(a+b)-bc(b+c)+ca(a-c)
    =ab(a+b)-b^2c-bc^2+a^2c-ac^2
    =ab(a+b)+(a^2c-b^2c)-(ac^2+bc^2)
    =ab(a+b)+c(a^2-b^2)-c^2(a+b)
    =ab(a+b)+c(a+b)(a-b)-c^2(a+b)
    =(a+b)[ab+c(a-b)-c^2]
    =(a+b)(ab+ac-bc-c^2)
    =(a+b)[a(b+c)-c(b+c)]
    =(a+b)(b+c)(a-c)
    C=ab(a+b)+bc(b+c)+ca(c+a)+3abc
    =ab(a+b)+bc(b+c)+ca(c+a)+abc+abc+abc
    =[ab(a+b)+abc]+[bc(b+c)+abc]+[ca(c+a)+abc]
    =ab(a+b+c)+bc(a+b+c)+ac(a+b+c)
    =(a+b+c)(ab+bc+ac)

  2. Giải đáp:
    B = ab(a + b) – bc(b + c) + ca(a – c)
    = ab[(a – c) + (b + c)] – bc(b + c) + ca(a – c)
    = [ab(a – c) + ca(a – c)] + [ab(b + c) – bc(b + c)]
    = (a – c)(ab + ca) + (b + c)(ab – bc)
    = (a – c)(b + c) a + (b + c)(a – c)b
    = (a – c)(b + c)(a + b)
    C = ab(a + b) + bc(b + c) + ca(c + a) + 3abc
    = ab(a + b) + bc(b + c) + ca(c + a) + abc + abc + abc
    = [ab(a + b) + abc] + [bc(b + c) + abc] + [ca(c + a) + abc]
    = ab(a + b + c) + bc(b + c + a) + ca(a + b + c)
    = (a + b + c)(ab + bc + ca)

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