@ @¶ìÿa@óÝy‹¾a@ u@ @QQP 4x x −1− x +1+1 = 0 [AHSME 1957] ( ) 4 () 5( ) 5( ) 4() 5 4 [AHSME 1959] ( ) sr 6() r2 + s2 x 2 − 3x + 1 = 0 : 4 () () 24 ( ) () 4 () . 9 . [MAΘ1990 ] ( ) 5( ) 4( ) 3 () [MAΘ 1990] ( 301 . ) .1 22 ( ) 21 ( ) 17 ( )