Tính hợp lí: a, 17/18 : -11/3 + 31/8 . -3/11 +4/11 b, 7/15 . -23/45 + 7/15 . -22/45 – 8/15

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1. Giải đáp + Lời giải và giải thích chi tiết:

   a, 17/18 : ${\displaystyle \frac{-11}{3}}$ + 31/8 . ${\displaystyle \frac{-3}{11}}$ + 4/11

   = 17/18 . ${\displaystyle \frac{-3}{11}}$ + 31/8 . ${\displaystyle \frac{-3}{11}}$ + 4/11

   = ${\displaystyle \frac{-17}{66}}$ + ${\displaystyle \frac{-93}{88}}$ + 4/11

   = ${\displaystyle \frac{-68}{264}}$ + ${\displaystyle \frac{-279}{264}}$ + 4/11

   = ${\displaystyle \frac{-347}{264}}$ + 4/11

   = ${\displaystyle \frac{-347}{264}}$ + 96/264

   = ${\displaystyle \frac{-251}{264}}$

   b, 7/15 . ${\displaystyle \frac{-23}{45}}$ + 7/15 . ${\displaystyle \frac{-22}{45}}$ – 8/15

   = 7/15 . ( ${\displaystyle \frac{-23}{45}}$ – 22/45 ) – 8/15

   = 7/15 . ${\displaystyle \frac{-45}{45}}$ – 8/15

   = 7/15 . -1 – 8/15

   = ${\displaystyle \frac{-7}{15}}$ + 8/15

   = ${\displaystyle \frac{-15}{15}}$

   = -1

    

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