Rút gọn biểu thức: a,(x-3)^2-(x+1)(x-5) b,(x-1)(x^2+x+1)-(2x+1)(1-2x) c,x^2-2x:(-1/2x)-(x^2-2x+1):(x-1)

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1. a) `(x-3)^2 -(x+1)(x-5) = x^2-6x+9-x^2+4x+5 = -2x+4`

   b) `(x-1)(x^2+x+1)-(2x+1)(1-2x) = (x^3-1)-[(2x)^2-1^2]`

   `= x^3-1-4x^2+1=x^3-4x^2`

   c) `x^2-2x : (-1/2 x) – (x^2-2x+1):(x-1)`

   `= x^2 + 4x^2 – (x-1)^2 :(x-1) = 5x^2 – x+1 `

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2. `a,(x-3)^2-(x+1)(x-5)`

   `=(x^2-6x-9)-(x^2-5x+x-5)`

   `=(x^2-6x-9)-(x^2-6x-5)`

   `=x^2-6x-9-x^2+6x+5`

   `=12x-4`

   `b,(x-1)(x^2+x+1)-(2x+1)(1-2x)`

   `=x^2+x^2+x-x^2-x-(2x-4x+1-2x)`

   `=x^2+x^2+x-x^2-x-2x+4x-1+2x`

   `=x^2+4x-1`

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