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@ @@Hßìÿaö§aI@†a‡Èÿa@óî‹Åä@

     n                      27 ( )         an [MAӨ 2011] ( )

     29 ( )                                          a1 + a2 + ... + a10

                                               25 ( ) 23 ( )

                                     :( )
. a1 + a2 + ... + a10 = 1+ 2 + 2 + 3 + 2 + 4 + 2 + 4 + 3 + 4 = 27

mn = 40                                                nm          ()

        13 ( )              m +n                     2m + 3n = 31

                            12 ( )              8( ) 5()

                . n = 40               mn = 40  :( )

                       m

                2m  +      40     =  31
                       3  m   

                2m 2 − 31m +120 = 0

                (2m −15) (m − 8) = 0

.m =8                           m . m = 15             m =8

                                                    2     .n =5

                                . m + n = 8 + 5 =13

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