Toán Lớp 8: A) 6x .(2x+4x²)-3 .(2x²+3x³)+1 B) 2/3x² (3/2x +3/4)-x.(x²+x+2) C) (3x²-6x+2).2x – x .(2x²-3x +4)

0 bình luận về “Toán Lớp 8: A) 6x .(2x+4x²)-3 .(2x²+3x³)+1 B) 2/3x² (3/2x +3/4)-x.(x²+x+2) C) (3x²-6x+2).2x – x .(2x²-3x +4)”

1. a)

   6x(2x + 4x^2) – 3(2x^2 + 3x^3) + 1

   = 12x^2 + 24x^3 – 6x^2 – 9x^3 + 1

   = 6x^2 + 15x^3 + 1

   b)

   2/3x^2(3/2x + 3/4) – x(x^2 + x + 2)

   = x^3 + 1/2x^2 – x^3 – x^2 – 2x

   = -1/2x^2 – 2x

   c)

   (3x^2 – 6x + 2) . 2x – x(2x^2 – 3x + 4)

   = 6x^3 – 12x^2 + 4x – 2x^3 + 3x^2 – 4x

   = 4x^3 – 9x^2

2. Giải đáp+Lời giải và giải thích chi tiết:

    A = 6x(2x + 4x²) – 3(2x² + 3x³) + 1

       = 12x² + 24x³ – 6x² – 9x³ + 1

      = 15x³ + 6x² + 1

   B = $\frac{2}{3}$ x²($\frac{3}{2}$ x + $\frac{3}{4}$) – x(x² + x + 2)

      = x³ + $\frac{1}{2}$ x² – x³ – x² – 2x

     = $\frac{-1}{2}$ x² – 2x

   C = (3x² – 6x + 2).2x – x(2x² – 3x + 4)

      = 6x³ – 12x² + 4x – 2x³ + 3x² – 4x

      = 4x³ – 9x²