Bài 1:Tìm x;biết: a,x=-15/21:2 b,2/3.x+4,5=0 c,x+1/19+x+2/18+x+3/17=x+4/16+x+5/15+x+6/14

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1. a, x=-15/21:2

   x=-15/21*1/2

   x=-15/42=-5/14

   b,

   2/3*x+4,5=0

   2/3*x       =0-4,5

   x              =-4.5 : 2/3

   x              =-4.5/1*3/2

   x             = -27/4=-6,75

   c,

   x+1/19+x+2/18+x+3/17=x+4/16+x+5/15+x+6/14

   =x+1/19+x+2/18+x+3/17+x+4/16+x+5/15+6/14

   <=>((x+1/19+x+2/18+x+3/17+3))=((x+4/16+x+5/15+x+6/14+3))

   <=>((x+1/19+1)+(x+2/18+1)+(x+3/17+1))-((x+4/16+1)+(x+5/15+1)+(x+6/14+1))=0

   <=>((x+1/19+19/19)+(x+2/18+18/18)+(x+3/17+17/17))–((x+4/16+16/16)+(x+5/15+15/15)+(x+6/14+14/14))=0

   <=>(x+20/19+x+20/18+x+20/17)-(x+20/16+x+20/15+x+20/14)=0

   <=>(x+20)*(1/19+1/18+1/17-1/16-1/15-1/14)=0

   vì 1/19+1/18+1/17-1/16-1/15-1/14 khác 0

   =>x+20=0

   =>x=-20

   dấu ngoặc tròn tui để in đậm và nghiêng thực ra là dấu ngoặc vuông nhaaa :>

    

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