Thực hiện phép tính: a, (x+3)(x-3)-(x-2)(x+5) b, (2x^3-11x^2+6x-5):(2x^2-x+1) c, (x+1)(x^2-x+1)-(3+x)(9-3x+x^2) d, (2x+3)(4x^2-6x+9)-2(4x^3-1)

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

   $=x^2-9-(x^2+5x-2x-10)$

   $=x^2-9-x^2-3x+10$

   $=1-3x$

   b, $\dfrac{2x^3-11x^2+6x-5}{2x^2-x+1}$

   $=\dfrac{x^3-10x^2-x^2+5x+x-5}{2x^2-x+1}$

   $=\dfrac{x^2(x-5)-x(x-5)+(x-5)}{2x^2-x+1}$

   $=\dfrac{(x-5)(x^2-x+1)}{2x^2-x+1}$

   $=x-5$

   c, $(x+1)(x^2-x+1)-(3+x)(9-3x+x^2)$

   $=x^3+1-(27+x^3)$

   $=x^3+1-27-x^3$

   $=-26$

   d, $(2x+3)(4x^2-6x+9)-2(4x^3-1)$

   $=8x^3+27-8x^3+2$

   $=29$

   e, $\dfrac{x^3-3x^2y+3xy^2-y^3}{x^2-2xy+y^2}$

   $=\dfrac{(x-y)^3}{(x-y)^2}$

   $=x-y$

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