(x+3)^2-(x-3)^2-12x chuwngs minh bieu thuc nay ko phu thuoc vao bien

1 bình luận về “(x+3)^2-(x-3)^2-12x chuwngs minh bieu thuc nay ko phu thuoc vao bien”

1. (x+3)^2-(x-3)^2-12x

   = (x^2+2.x.3+3^2)-(x^2-2.x.3+3^2)-12x

   = (x^2+6x+9)-(x^2-6x+9)-12x

   = x^2+6x + 9-x^2+6x-9-12x

   = (x^2-x^2)+(6x+6x-12x)+(9-9)

   = 0+0+0

   = 0(đpcm)

    

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