Find the rule for the sequence:

4.2, 2.6, 1, -.06, -2.2

2 answers

put it in nth term
If you take the difference between consecutive terms, you will find that the difference is constant at -1.6.
So it is an arithmetic sequence.

T(n)=K-1.6n
T(1)=4.2
so 4.2=K-1.6*1 => K=4.2+1.6=5.8, or

T(n)=5.8-1.6n
Check: third term
T(3)=5.8-1.6*3=1.0 OK.