3sur2 diviser par (1sur7-1sur3)-

[tex] \frac{3}{2}:( \frac{1}{7}- \frac{1}{3}) = \frac{3}{2}:( \frac{3}{21}- \frac{7}{21})= \frac{3}{2}: \frac{-4}{21}= \frac{3}{2}\times \frac{-21}{4}= \frac{-63}{8} [/tex]

__3/2 __ = _______3/2_________  =          3/2___ = 3/2 = 3/2 : - 4/21 = 3/2 x - 21/4 =
1/7 - 1/3      1 x 3 / 7 x 3 - 1 x 7 / 3 x 7        3/21 - 7/21  - 4/21
- 63/8