# Sequence help!

• January 8th 2008, 04:02 AM
nugiboy
Sequence help!
Im really confused on this question:

http://i137.photobucket.com/albums/q...tiger/HALP.jpg

I know how to do all the geometric and arethmatic formulae, but i just can't work out the first 4 terms from that formula given. Any suggestions?
• January 8th 2008, 04:08 AM
mr fantastic
Quote:

Originally Posted by nugiboy
Im really confused on this question:

http://i137.photobucket.com/albums/q...tiger/HALP.jpg

I know how to do all the geometric and arethmatic formulae, but i just can't work out the first 4 terms from that formula given. Any suggestions?

Hmmm, lessee now ..... If we let r = 1, the rule tells us that $a_{2} = a_1 + 3$. But holy cow ...... $a_1 = 4$. So $a_2 = 7$. Hmmmmm ..... can you play this game when r = 2? r = 3?
• January 8th 2008, 04:16 AM
nugiboy
Quote:

Originally Posted by mr fantastic
Hmmm, lessee now ..... If we let r = 1, the rule tells us that $a_{2} = a_1 + 3$. But holy cow ...... $a_1 = 4$. So $a_2 = 7$. Hmmmmm ..... can you play this game when r = 2? r = 3?

The answer book says its 4 , 7 , 10 , 13
Which is obviously + 3, but i dont understand how the formula shows that exactly.

I can see how the first one is 4, as it says $a_1 = 4$, but i cant see how it shows + 3.
• January 8th 2008, 04:32 AM
mr fantastic
Quote:

Originally Posted by nugiboy
The answer book says its 4 , 7 , 10 , 13
Which is obviously + 3, but i dont understand how the formula shows that exactly.

I can see how the first one is 4, as it says $a_1 = 4$, but i cant see how it shows + 3.

$a_{r+1} = a_r$ + 3. Translation: The next term is 3 more than the previous term. That's what the + 3 in the given rule means!!! What do you think the + 3 means?