Find n, if the ratio of the fifth term from the beginning to the fifth term from the end in the expansion of  isÂ
Co-efficient of  in the expansion ofÂ
             ...(i)
Also, co-efficient of  in the expansion ofÂ
                                       (∵Â
  )
                                                  ...(ii)    Â
Hence, from (i) and (ii), the co-efficient of  is equal to the co-efficient ofÂ