Question

FAN & MEDAL. - 9th Grade Integrated Mathematics

1. What are the first three terms of the sequence a1 = 1 and an = 4(an-1)^3?

A. 1,4, 256
B. 1, 256, 500
C. 4, 32, 108
D. 4, 8, 256

Answer 1

Here's a picture for better visual on the problem: http://i.gyazo.com/36cbdab5bc67fb4cd3860fcc2d7ee1b0.png

Answer 2

You substitute an-1 with the value for a1 and evaluate that expression to get a2. You then do the same thing again with a2 to get a3.

Answer 3

My first guess on the question would be A. 1, 4, 256. I don't really quite understand the equation but I kind of get an idea what you're saying.

Answer 4

Maby an example will help:
\[a_1=3\]\[a_n = 2(a_{n-1})^2\]
\[a_2 = 2(a_{2-1})^2 = 2(a_{1})^2 = 2(3)^2 = 2 \times 9 = 18\]
\[a_3 = 2(a_{3-1})^2 = 2(a_{2})^2 = 2(18)^2 = 2 \times 324 = 648\]

Answer 5

And yes it's A :)

Answer 6

Wow, I'll definitely keep your example in mind. Thank you very much, @Lyrae

Answer 7

Anytime :)