6x" - 7x + 5= ( 1/24 )( 144x" - 168x + 120 )= ( 1/24 )[ ( 12x )" - 14( 12x ) + 7" - 49 + 120 ]= ( 1/24 )[ ( 12x - 7 )" + 71 ]这样要分解因式,就只能在复数范围= ( 1/24 )[ ( 12x - 7 )" - ( - 71 ) ]= ( 1/2...