Find a Formula for A_n for the Arithmetic Sequence $a _ { n } = 7 \left( - \frac { 1 } { 8 } \right) ^ { n - 1 }$

Multiple Choice

Find a formula for a_n for the arithmetic sequence. ?
A₁ = 7,d = -8
?

A) $a _ { n } = 7 \left( - \frac { 1 } { 8 } \right) ^ { n - 1 }$
B) $a _ { n } = - 8 + 7 ( n - 1 )$
C) $a _ { n } = 7 - 9 n$
D) ? $$a _ { n } = 15 - 8 n$$
E) $a _ { n } = 7 - 8 ^ { n - 1 }$