Given Are the First Three Terms of a Sequence That $a _ { 1 } = 9 ; d = - 12$

Multiple Choice

Given are the first three terms of a sequence that is arithmetic. Find a1 and d.
-9, 13, 17

A) $a _ { 1 } = 9 ; d = - 12$
B) $\mathrm { a } _ { 1 } = 9 ; \mathrm { d } = 12$
C) $a _ { 1 } = 9 ; d = - 4$
D) $a _ { 1 } = 9 ; d = 4$