a)( 5x-2x)(3x+4y)-(4x+y) ^2 B) (3x-2y)^2+(5x-3y)(3y+5x) C) (x-1)(x^2+x+1)-(x+1)(x^2-x+1) D) (x+1)^3 – x(x-1)^2 + 6

0 bình luận về “a)( 5x-2x)(3x+4y)-(4x+y) ^2 B) (3x-2y)^2+(5x-3y)(3y+5x) C) (x-1)(x^2+x+1)-(x+1)(x^2-x+1) D) (x+1)^3 – x(x-1)^2 + 6”

1. Đáp án + Giải thích các bước giải:

   `a)` `(5x-2x)(3x+4y)-(4x+y)^2` $\\$ `= 3x(3x+4y)-[(4x)^2+2*4x*y+y^2]` $\\$ `= 9x^2 + 12xy – (16x^2+8xy+y^2)` $\\$ `= 9x^2+ 12xy – 16x^2 – 8xy – y^2 = -7x^2+4xy-y^2`

   `b)` `(3x – 2y)^2+(5x-3y)(3y+5x)` $\\$ `= (3x)^2-2*3x*2y+(2y)^2 – (3y – 5x)(3y + 5x)` $\\$ `= 9x^2-12xy+4y^2-(9y^2-25x^2)` $\\$ `= 9x^2 – 12xy + 4y^2 – 9y^2 + 25x^2 = 34x^2-5y^2-12xy`

   `c)` `(x – 1)(x^2 + x + 1)-(x+1)(x^2-x+1)` $\\$ `= x^3 -1 – (x^3+1)=x^3-1-x^3-1=-2`

   `d)` `(x + 1)^3-x(x-1)^2+6` $\\$ `=x^3+3x^2+3x+1-x(x^2-2x+1)+6` $\\$ `= x^3 + 3x^2 + 3x + 1 – x^3 + 2x^2 – x + 6` $\\$ `= 5x^2+2x+7`

    

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