# What is the 20th term of the arithmetic sequence 2, –4, –10, … ?

##### 3 Answers

#### Explanation:

the nth term of an AP

is

here we have

and it is seen that

#### Explanation:

If the sequence is denoted by the series

then

Setting

so that the first term is

we have

For

#### Explanation:

The terms in the sequence

You can keep writing the terms until you get to the 20th, but that is not a very mathematical way of doing it and would be VERY time-consuming if you were asked for the 200th term for example.

Find the rule for the sequence... called

If the difference is

You need to adjust the rule to start at the correct number,

When

But the first term must be

Check if

Check if

Now find the 20th term: