a) 12x 2x ______ + _____ x^2-9 x+3 b) 1-x x-2 ______ + _______ x-3 x-3

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1. `(12x)/(x^2-9)+(2x)/(x+3)`         Điều kiện xác định: `x\ne±3`

   `=(12x)/((x-3)(x+3))+\frac{2x(x-3)}{(x-3)(x+)}`

   `=\frac{12x+2x^2-6x}{(x-3)(x+3)}`

   `=\frac{2x^2+6x}{(x-3)(x+3)}`

   `=\frac{2x(x+3)}{(x-3)(x+3)}`

   `=\frac{2x}{x-30}`

   `b)` `\frac{1-x}{x-3}+\frac{x-2}{x-3}`      Điều kiện xác định: `n\ne3`

   `=\frac{1-x+x-2}{x-3}`

   `=\frac{-1}{x-3}`

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2. ` a) ` ` \frac{12x}{x^2 – 9} + \frac{2x}{x + 3} `

   ` = \frac{12x + 2x(x – 3)}{(x – 3)(x + 3)} `

   ` = \frac{12x + 2x^2 – 6x}{(x – 3)(x + 3)} `

   ` = \frac{2x^2 – 6x}{(x – 3)(x + 3)} `

   ` = \frac{2x(x – 3)}{(x – 3)(x + 3)} `

   ` = \frac{2x}{x + 3} `

   ` b) ` ` \frac{1 – x}{x – 3} + \frac{x – 2}{x – 3} `

   ` = \frac{1 – x + x – 2}{x – 3} `

   ` = \frac{-1}{x – 3} `

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