(2x-3)×(x^2-x+3) b,(x+2)^3-(x-1)^3-9x(x+1)

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1. a. (2x-3)(x²-x+3)

   = 2x³-2x²+6x-3x²+3x-9

   = 2x³-5x²+9x-9

   <=> x(2x²-5x+9) = 9

   <=> x=9 hoặc 2x²-5x+9=9

   <=> x=9 hoặc x= 5/4

   b. (x+2)³-(x-1)³-9x(x+1)

   = x³ + 6x² + 12x + 8 – (x³ – 3x² + 3x – 1) – (9x² + 9x)

   = x³ + 6x² + 12x + 8 – x³ + 3x² – 3x + 1 – 9x² – 9x

   = 9

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