Tìm x : a) 12/15=-8/x b)4 3/7 – 3/7.x=-9/14

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1. a) `12/15 = -8/x`

   `4/5 = -8/x`

   `-8/(-10) = -8/x`

   `x=-10`

   b) `4(3)/7 – 3/7 . x =-9/14`

   `4 + 3/7 – 3/7 .x = -9/14`

   `-3/7 .x = -71/14`

   `x = -71/14 : (-3/7)`

   `x=71/6`

   Trả lời

2. Giải thích các bước giải:

   `a)`
   `12/15=-8/x`
   `=>12.x=15.(-8)`
   `=>12.x=-120`
   `=>x=-120:12`
   `=>x=-10`
   Vậy `x=-10`
   `b)`
   `4 3/7 – 3/7 . x=-9/14`
   `=>31/7 – 3/7 . x = -9/14`
   `=>3/7 . x=31/7+9/14`
   `=>3/7 . x=62/14+9/14`
   `=>3/7 . x=71/14`
   `=>x=71/14:3/7`
   `=>x=71/14 . 7/3`
   `=>x=71/6`
   Vậy `x=71/6`

   Trả lời