1.Thu gọn a) 3x ( 4x – 3 ) – 2x ( 6x + 5 ) b) 4x ( 3x^2 –x ) – 2x ( 6x^2 – 3x + 1 ) c) 2x ( x^2 – 3 ) – 3( 4x^2 – 2x + 1 )

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1. Đáp án:

    

   Giải thích các bước giải:

   `a) 3x ( 4x – 3 ) – 2x ( 6x + 5 )`

   `=x[3(4x-3)-2(6x+5)]`

   `=x(12x-9-12x-10)`

   `=-19x`

   `b) 4x ( 3x^2 –x ) – 2x ( 6x^2 – 3x + 1 )`

   `=2x[2( 3x^2 –x ) – ( 6x^2 – 3x + 1 )]`

   `=2x(6x^2-2x-6x^2+3x-1)`

   `=2x.(x-1)`

   `c) 2x ( x^2 – 3 ) – 3( 4x^2 – 2x + 1 )`

   `=2x^3-6x-12x^2+6x-3`

   `=2x^3-12x^2-3`

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2. a) 3x ( 4x – 3 ) – 2x ( 6x + 5 )
   ⇒ 12x^2 – 9x – 12^2 – 10x
   ⇒            -19x 

   b) 4x ( 3x^2 –x ) – 2x ( 6x^2  –  3x + 1 )
   ⇒ 12x^3  –  4x^2 – 12x^3 + 6x^2 – 2x
   ⇒             2x^2 – 2x

   c) 2x ( x^2 – 3 ) – 3( 4x^2 – 2x + 1 )
   ⇒ 2x^3 – 6x – 12x^2 + 6x – 3
   ⇒       2x^3 – 12x^2 – 3

   Học tốt^^

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