The first five terms of an arithmetic sequence are shown below: 20, 17, 14, 11, 8, . . let n represent the term number and f(n) the term in the sequence.

The rule of an arithmetic sequence:

- first term

- a difference  

We have:

substitute:

f(n) = -3n + 23

step-by-step explanation:

1. practice, practice & more practice

2. review errors

3. master the key concepts

do not try to memorise the processes.

4. understand your doubts.

5. create a distraction free study environment

6. create a mathematical dictionary

7. apply maths to real world problems.

irrational, cannot