我认为如下 2X - 1 2X - 2 + 1 2( X - 1 ) + 1 2( X - 1 ) 1 1 Y= ------------- = ----------------- = ----------------------- = ------------------ + ------------------ = 2 + --------- X - 1 X - 1 X - 1 ( X - 1 ) ( X -1 ) (X-1) X越大,Y越小.