a) (x-y) ( x+ y) – (x – y) ^2 + ( x+ y)^2 b) (x + 3) ( x^2 – 3x +1)^9 c) (x – 5) ( x^2 – 5x + 25) d) ( 2x – 1) ( 4x^2 + 2x + 1) – 4x (2x^2 -1)

0 bình luận về “a) (x-y) ( x+ y) – (x – y) ^2 + ( x+ y)^2 b) (x + 3) ( x^2 – 3x +1)^9 c) (x – 5) ( x^2 – 5x + 25) d) ( 2x – 1) ( 4x^2 + 2x + 1) – 4x (2x^2 -1)”

1. $a)(x-y)(x+y)-(x-y)^2+(x+y)^2_{}$

   $⇔x^2-y^2-(x^2-2xy+y^2)+x^2+2xy+y^2_{}$

   $⇔x^2-x^2+2xy-y^2+x^2+2xy_{}$

   $⇔4xy-y^2+x^2_{}$

   $c)(x-5)(x^2+5x+25)_{}$

   $⇔x^3-5^3_{}$

   $⇔x^3-125_{}$

   $d)(2x-1)(4x^2+2x+1)-4x(2x^2-1)_{}$

   $⇔8x^3-1-8x^3+4x_{}$

   $⇔4x-1_{}$  

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2. Đáp án:

    

   Giải thích các bước giải:

    a) $(x-y) ( x+ y) – (x – y)^2 + ( x+ y)^2$

   $=x^2 -y^2 -(x^2 -2xy+y^2) +(x^2+2xy+y^2)$

   $=x^2 -y^2 -x^2 +2xy -y^2 +x^2+2xy+y^2$

   $=x^2+4xy -y^2$

   b)$ (x + 3) ( x^2 – 3x +1)^9$

   đề sai chăng.

   c) sửa chút chỗ -5x thành 5x

   $(x – 5) ( x^2 + 5x + 25)$

   $=x^3 -125$

   d) $( 2x – 1) ( 4x^2 + 2x + 1) – 4x (2x^2 -1)$

   $=8x^3 -1 -8x^3 +4x$

   $=4x-1$

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