( 2x + 5 ) ( x^2 -4x + 7 ) ( 3x -8 ) ( -2x^2 + x + 5 ) (3x – 2 ) ( 9x^2 + 6x + 4 )

2 bình luận về “( 2x + 5 ) ( x^2 -4x + 7 ) ( 3x -8 ) ( -2x^2 + x + 5 ) (3x – 2 ) ( 9x^2 + 6x + 4 )”

1. Cii

   (2x+5)(x^2-4x+7)

   =2x( x^2 -4x + 7 )+5( x^2 -4x + 7 )

   =2x^3-8x^2+14x+5x^2-20x+35

   =2x^3-3x^2-6x+35

   ( 3x -8 ) ( -2x^2 + x + 5 )

   =3x( -2x^2 + x + 5 )-8( -2x^2 + x + 5 )

   =-6x^3+3x^2+15x+16x^2-8x-40

   =-6x^3+19x^2+7x-40

   (3x – 2 ) ( 9x^2 + 6x + 4 )

   =3x( 9x^2 + 6x + 4 )-2( 9x^2 + 6x + 4 )

   =27x^3+18x^2+12x-18x^2-12x-8

   =27x^3-8

    

   Trả lời
2. Giải đáp:

    

   Lời giải và giải thích chi tiết:

    a) 

   (2x+5)(x^2 -4x + 7 )  

   = 2x^3 – 8x^2 + 14x + 5x^2 – 20x + 35  

   = 2x^3 + ( – 8x^2 + 5x^2) + ( 14x – 20x )   

   = 2x^3 + – 3x^2 +  – 6x + 35

   b) 

   (3x-8)(-2x^2 + x + 5 )  

   = -6x^3 + 3x^2 + 15x +16x^2 – 8x – 40  

   = -6x^3 + ( 3x^2 + 16x^2 ) + ( 15x – 8x ) – 40

   = -6x^3 + 19x^2 + 7x – 40  

   c) 

   (3x-2)(9x^2 + 6x + 4 )  

   = 27x^3 + 18x^2 + 12x – ( 18x^2 + 12x + 8 )  

   = 27x^3 + 18x^2 + 12x – 18x^2 – 12x – 8  

   = 27x^3 + ( 18x^2 – 18x^2) + ( 12x – 12x ) – 8  

   = 27x^3 – 8

   Trả lời