根据题意得x1+x2=- 1 3 ,x1?x2=- 1 3 ,( 1 x1 )2+( 1 x2 )2= x12+x22 x12?x22 = (x1+x2)2?2x1x2 (x1x2)2 = (? 1 3 )2?2×(? 1 3 ) (? 1 3 )2 =7.故答案为7.