Question

write an explicit formula for the sequence then find the fifth term
a_1 = 3, r = -3

a. a_n = 3*(-3)^n-1; 243
b. a_n = -3*(3)^n-1; -243
c. a_n = 3*(3)^n; 243
d. a_n = 3*(-3)^n; -729

thank u!!

Answer 1

for any geometric sequence a_n = a*r^(n-1)
so plug in your numbers.