Question

Which one is a rule for the nth term of the sequence 3, 15, 75, 375...?

Answer 1

note that each term is obtained from previous by multiplying by 5

Answer 2

A. an = 3(5)n − 1 B. an = 5(3)n − 1 C. an = 3(5)n + 1 D. an = 5(3)n + 1

Answer 3

this is called a geometric sequence

Answer 4

those are my answer choices

Answer 5

try plugging n = 2, 3 and 4 into A and see if you get 15,75 and 375

Answer 6

eg n=2: 3(5)^(2-1) = 3*5^1 = 3*5 = 15 - that one works
now try n=3

Answer 7

do you see what i'm doing?