Posted by **Anonymous** on Saturday, May 9, 2009 at 10:02am.

help me with sequences problem.So if the sequence is 2,5,10,17,26

+3 +5 +7 +9 1st difference

+2 +2 +2 2nd difference

then the nth term can be worked out by writing out :

n 1 2 3 4

n squared 1 4 9 16

original sequence 2 5 10 17

nth term= n squared+1

but what about this question:

8, 10, 14, 20, 28

+2 +4 +6 +8

+2 +2 +2

n 1 2 3 4

n squared 1 4 9 16

original sequence 8 10 14 20 the number you have to add to n squared is different every time so does anybody know how too get the nth term for this sequence?

- math -
**TchrWill**, Sunday, May 10, 2009 at 10:27am
help me with sequences problem.So if the sequence is 2,5,10,17,26

+3 +5 +7 +9 1st difference

+2 +2 +2 2nd difference

then the nth term can be worked out by writing out :

n 1 2 3 4

n squared 1 4 9 16

original sequence 2 5 10 17

nth term= n squared+1

but what about this question:

8, 10, 14, 20, 28

+2 +4 +6 +8

+2 +2 +2

n 1 2 3 4

n squared 1 4 9 16

original sequence 8 10 14 20 the number you have to add to n squared is different every time so does anybody know how too get the nth term for this sequence?

With 2nd differences being equal, the general expression is of the form an^2 + bn + c

8, 10, 14, 20, 28

.+2. +4. +6. +8

...+2. +2. +2

a(1)^2 + b(1) + c = 8

a(2)^2 + b(2) + c = 10

a(3)^2 + b(3) + c = 14

a + b + c = 8

4a + 2b + c = 10

9a + 3b + c = 14

Solving, a = 1, b = -1 and c = 8.

Thus, the nth term derives from N = n^2 - n + 8.

## Answer This Question

## Related Questions

- Sequence - Find the common difference and a formula formula for the nth term of ...
- math - find the rule for the Nth term of the arithmetic sequence. 11/2, 25/6, 17...
- arithmetic - THE SUM OF THE 2ND AND 5TH TERMS OF AN A.P IS 42. IF THE DIFFERENCE...
- Math - 1.) What is the formula for the nth term of the arithmetic sequence that ...
- MATH!!!! SEQUENCES!!! - Find out a formula for the Nth term of each of the ...
- Urgent math - how do I do this can any body show me how? An arithmetic sequence ...
- Alg 2/trig - I am doing Geometric sequences, but I cannot figure out how to find...
- Maths: Sequences need help - The nth term of a sequences of v1,v2,v3 is given by...
- math - in an AP the 10th term is 54 and 5th term is 4 times the 2nd term . Find ...
- Algebra - True or False 1. – 5, – 5, – 5, – 5, – 5, … is an arithmetic sequence...

More Related Questions