51.2,64,80,(),()找規律,填數.怎麼寫?還有(),(),19.8,13.2,8.8也是找規律填數,怎麼寫?

51.2,64,80,(),()找規律,填數.怎麼寫?還有(),(),19.8,13.2,8.8也是找規律填數,怎麼寫?

38.7-28.6-19.8-13.2-8.8