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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 8: 1. Tính: a. (4x ² + 5x – 1) (2x ³ – 3x) b. (2x ² + 3) ²

Toán Lớp 8: 1. Tính:
a. (4x ² + 5x – 1) (2x ³ – 3x)
b. (2x ² + 3) ²

Comments ( 2 )

  1. a) (4x^2+5x-1)(2x^3-3x)
    =4x^{2}.2x^3+5x.2x^3-1.2x^3-4x^{2}.3x-5x.3x+1.3x
    =8x^5+10x^4-2x^3-12x^3-15x^2+3x
    =8x^5+10x^4-14x^3-15x^2+3x
    b) (2x^2+3)^2
    =(2x^2)^2+2.2x^{2}.3+3^2
    =4x^4+12x^2+9
    * (a+b)^2=a^2+2ab+b^2
     

  2. a) (4x^2 +5x-1)(2x^3-3x)
    =2x^3 .(4x^2 +5x-1) – 3x.(4x^2 +5x-1)
    =8x^5 + 10x^4 – 2x^3 – 12x^3 – 15x^2 +3x
    =8x^5 + 10x^4 – 14x^3 – 15x^2 + 3x
    b) (2x^2 + 3)^2
    =(2x^2)^2 + 2.2x^2 .3 + 3^2
    =4x^4 + 12x^2 + 9
    #wcdi

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222-9+11+12:2*14+14 = ? ( )