Cho 2 đa thức : A(x) = 3x³ – x² + 4x – 12vaf B (x) = 3x³ – 4x² – 7x + 8 Tính: a/ A(x) + B(x) b/ 3.A(x) – 2.B(x)

1 bình luận về “Cho 2 đa thức : A(x) = 3x³ – x² + 4x – 12vaf B (x) = 3x³ – 4x² – 7x + 8 Tính: a/ A(x) + B(x) b/ 3.A(x) – 2.B(x)”

1. a, A(x) +B(x)

   = 3x^3 – x^2 + 4x – 12 + 3x^3 – 4x^2 – 7x + 8

   = (3x^3 + 3x^3)+(-x^2 – 4x^2)+(4x – 7x)+(-12 +8)

   = 6x^3 – 5x^2 – 3x – 20

   ——-

   b, 3.A(x) – 2B(x)

   = 3.(3x^3 – x^2 + 4x – 12) – 2.( 3x^3 – 4x^2 – 7x + 8)

   = 9x^3 – 3x^2 + 12x – 36 – 6x^3 + 8x^2 + 14x – 16

   = (9x^3 – 6x^3) +(-3x^2 + 8x^2) + (12x +14x)+(-36 -16)

   = 3x^3 + 5x^2 + 26x -52

    

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