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

Toán Lớp 8: Viết biểu thức sau dưới dạng TỔNG a)(1/2-x)^3 b)(2x-1)^3

Toán Lớp 8: Viết biểu thức sau dưới dạng TỔNG
a)(1/2-x)^3
b)(2x-1)^3

Comments ( 2 )

  1. a)
    (1/2-x)^3
    =(1/2)^3-3. (1/2)^2 . x+3. 1/2 . x^2-x^3
    =1/8-3/4x+3/2x^2-x^3
    =-x^3+3/2x^2+(-3)/4x+1/8
    b)
    (2x-1)^3
    =(2x)^3-3.(2x)^2 . 1+3.2x.1^2-1^3
    =8x^3+(-12x^2)+6x+(-1)

  2. a)(1/2-x)^3
    =(1/2)^3-3.(1/2)^2.x+3.1/2.x^2-x^3
    =1/8-3. 1/4.x+3. 1/2.x^2-x^3
    =1/8-3/4x+3/2x^2-x^3
    =(-x^3)+3/2x^2+(-3)/4x+1/8
    b)(2x-1)^3
    =(2x)^3-3.(2x)^2.1+3.2x.1^2-1^3
    =8x^3-3.4x^2+3.2x-1^3
    =8x^3-12x^2+6x-1
    =8x^2+(-12x^2)+6x+(-1).

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