## anonymous 5 years ago write the nth term of the sequence 1, 4, 9, 16

1. anonymous

$\sum_{k=1}^{n}2(k-1)+1$

2. anonymous

What does that notation mean?

3. myininaya

the nth term is n^2

4. myininaya

since 1^2=1, 2^2=4, 3^2=9, 4^2=16,...,n^2

5. anonymous

so what would the nth term be?

6. anonymous

oh n^2 ok

7. anonymous

What about the sequence 3, 11, 31, 69, 131

8. anonymous

anyone there

9. anonymous

myininaya are you there?

10. myininaya

I'm trying to see the pattern

11. anonymous

The first differences would be 3, 20, 38, 62. The second differences would be 12, 18, 23 and 30. The third difference would be 6 for all of them

12. anonymous

Oh I meant 24 not 23

13. anonymous

Are you still there?

14. anonymous

That's funny. Both answers are correct. My answer was that the nth term was the sum of the first n odd natural numbers. So the first number is 1, the second is 1+3=4, the third is 1+3+5=9, the fourth is 1+3+5+7 = 16

15. anonymous

polpak did you get my second question?

16. anonymous

Yeah, looking at it, but these things are kinda lame cause there's a lot of different ways you can approach it.

17. anonymous

ok. tell me when you have an answer

18. anonymous

I don't get this stuff.