按规律填数.(1)3.4 6 8.6 ( ) 13.8 ( ) (2)18.9 15.6 12.3 ( ) ( ) 2.4

问题描述:

按规律填数.(1)3.4 6 8.6 ( ) 13.8 ( ) (2)18.9 15.6 12.3 ( ) ( ) 2.4

(1) 3.4 6 8.6 (11.2) 13.8 ( 16.4) 递加2.6
2.18.9 15.6 12.3 (9) (5.7) 2.4 递减3.3