Question

if $a_1 = 4$ and $a_n = -3a_{n - 1}$ then find the value of $a_4$.

Explanation:

Step1: Find $a_2$ using $a_1$

$a_2 = -3a_1 = -3(4) = -12$

Step2: Find $a_3$ using $a_2$

$a_3 = -3a_2 = -3(-12) = 36$

Step3: Find $a_4$ using $a_3$

$a_4 = -3a_3 = -3(36) = -108$

Answer:

$-108$