Step 1:

The sequence is $\"\"$ \ \

Find the $\"\"$ term.

The sequence is arithmetic sequence.

Calculate the common difference,

d = second term - first term

$\"\"$

First term $\"\"$

$\"\"$

Find the sum of the first $\"\"$ terms.

Number of terms $\"\"$ \ \

Calculate the sum of the sequence by using the formula.

$\"\"$

Solution: \ \

$\"\"$

\ \