# How do you find the sum of the arithmetic sequence given 8, 3, -2, -7, -12, ....., -57?

##### 1 Answer

**Step 1: Find the number of terms**

The nth term of an arithmetic sequence is given by

**Step 2: Apply the formula for sum:**

When dealing with arithmetic series, we will frequently use two formulas to help us find the sum. They are:

•

•

Since we know the first term, the last term and the number of terms, we have enough information to use the latter; this one is more efficient and easy to use than the first.

Hence, the sum of this arithmetic sequence is

**Practice exercises:**

- Determine the sum of the following sequence:

Hopefully this helps, and good luck!