Answer:
B. -18
Step-by-step explanation:
In order to find the fourth term of the sequence, first find second term, next, third term and finally fourth term.
[tex]a_n = - 6 + a_{(n - 1)} \\ \\ \implies \: a_2 = - 6 + a_{(2 - 1)} = - 6 + a_1 = - 6 + 0 \\ \\ \implies \: \pink{a_2 = - 6} \\ \\\: a_3 = - 6 + a_{(3 - 1)} = - 6 + a_2 = - 6 + ( - 6) \\ \\ \implies \: \purple{ a_3 = - 12}\\ \\\: a_4= - 6 + a_{(4 - 1)} = - 6 + a_3 = - 6 + ( - 12) \\ \\ \implies \: \huge { \red{a_4 = - 18}}[/tex]
Another way:
[tex]a_1=0[/tex]
[tex]a_2=-6[/tex](Calculated above)
[tex]a_3=-6+a_2=-6-6=-12[/tex]
[tex]a_4=-6+a_3=-6-12=-18[/tex]
