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

Toán Lớp 8: Rút gọn biểu thức: 1) (x+2)(x-2)-(x-3)(x+1) 2)$(x-2)^{3}$ -$x(x+1)(x-1)$$+6x(x-3)$

Toán Lớp 8: Rút gọn biểu thức:
1) (x+2)(x-2)-(x-3)(x+1)
2)$(x-2)^{3}$ -$x(x+1)(x-1)$$+6x(x-3)$

Comments ( 2 )

  1. 1)(x+2)(x-2)-(x-3)(x+1)
    =x^2-2^2-(x^2+x-3x-3)
    =x^2-4-x^2+2x+3
    =2x-1
    2)(x-2)^3-x(x+1)(x-1)+6x(x-3)
    =x^3-3.x^2 .2+3.x.2^2-2^3-x(x^2-1)+6x^2-18x
    =x^3-6x^2+12x-8-x^3+x+6x^2-18x
    =(x^3-x^3)+(-6x^2+6x^2)+(12x-18x+x)-8
    =7x-8.

  2. #laviken#
    1)(x+2)(x-2)-(x+3)(x+1)
    =x^2-2^2-(x^2+x-3x-3)
    =x^2-4-x^2+2x+3
    =2x-1
    2)(x-2)^3-x(x+1)(x-1)+6x(x-3)
    =x^3-6x^2+12x-8-x^3+x+6x^2-18x
    =7x-8
     

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

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