Find the Partial Sum $a _ { n } = ( n + 1 ) ( n - 5 )$

Multiple Choice

Find the partial sum.
-Find the sum of the first three terms of the sequence whose general term is $a _ { n } = ( n + 1 ) ( n - 5 )$ .

A) 25
B) 65
C) $- 17$
D) $- 25$