Question

If a1 = 7 and an = -2an-1 then find the value of a5

Answer 1

Answer:

$a_1 = 7 \\ a_n = - 2a_{n - 1} \\ a_2 = - 2a_1 = - 2(7) = - 14 \\ a_3 = - 2a_2 = - 2( - 14) = 28 \\ a_4 = - 2a_3 = - 2(28) = - 56 \\ a_5 = - 2a_4 = - 2( - 56) = 112$