\ \
The expression is . \ \
The sequence is an arithmetic sequence with first term . \ \
Find the sum . \ \
The sum of the first terms of an arithmetic sequence . \ \
. \ \
The sum of the series is .
![\"\"](\"/userfiles/image/steps_images/step1.JPG\")
\ \
\ \
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=c1d95c1031519ac510bad4820ac474b9.png\")
. \ \
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=1bff6c1a1ad54ddca41f647f95e2b802.png\")
is an arithmetic sequence with first term ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=3480869daffe471392b26d548658c8da.png\")
. \ \
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=22a5ca762df0a19294ed5a7d95cf1e09.png\")
. \ \
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=9d9525296c7189f71cd1cbb29d5a4593.png\")
terms of an arithmetic sequence ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=6707208ed5dfe6b04aaa9fe5f7ffbfe7.png\")
. \ \
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=0851a323652c542d29f0b0ab6a126136.png\")
\ \
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=c89d8b4f02e968939350cd74e221a3ab.png\")
\ \
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=b3ef106cfb7e7efc75af7e534dd85965.png\")
. \ \
![\"\"](\"/userfiles/image/steps_images/solution.JPG\")
\ \
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=92088137f9be421b0c94a643391832f7.png\")
.