Find the 4th Term -3 , -8 , -13

$- 3$ , $- 8$ , $- 13$

Step 1

This is an arithmetic sequence since there is a common difference between each term. In this case, adding $- 5$ to the previous term in the sequence gives the next term. In other words, $a_{n} = a_{1} + d (n - 1)$ .

Arithmetic Sequence: $d = - 5$

Step 2

This is the formula of an arithmetic sequence.

$a_{n} = a_{1} + d (n - 1)$

Step 3

Substitute in the values of $a_{1} = - 3$ and $d = - 5$ .

$a_{n} = - 3 - 5 (n - 1)$

Step 4

Simplify each term.

Apply the distributive property.

$a_{n} = - 3 - 5 n - 5 \cdot - 1$

Multiply $- 5$ by $- 1$ .

$a_{n} = - 3 - 5 n + 5$

Step 5

Add $- 3$ and $5$ .

$a_{n} = - 5 n + 2$

Step 6

Substitute in the value of $n$ to find the $n$ th term.

$a_{4} = - 5 \cdot 4 + 2$

Step 7

Multiply $- 5$ by $4$ .

$a_{4} = - 20 + 2$

Step 8

Add $- 20$ and $2$ .

$a_{4} = - 18$

Find the 4th Term -3 , -8 , -13

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