math

posted by .

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 -

    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.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Sequence

    Find the common difference and a formula formula for the nth term of the arithmetic sequence; 6, 2, -2, -6, -10,...a sub n = a)6-4n b)6-2n c)10-2n d)10-4n I think it is c but want to check. Ao is 10, then each term subtracts 4n from …
  2. math

    find the rule for the Nth term of the arithmetic sequence. 11/2, 25/6, 17/6, 3/2, 1/6..... If you change the denomators to 6, you should notice the numerators follow the sequence: 33,25,17,9,1,...which is an arithmetic sequence with …
  3. Alg 2/trig

    I am doing Geometric sequences, but I cannot figure out how to find the Nth term of a geometric sequence. The problem is A1 = 64, Ak+1 = 1/2Ak (That is supposed to be A sub one, A sub k + 1, etc.) The formula for finding the equation …
  4. arithmetic

    THE SUM OF THE 2ND AND 5TH TERMS OF AN A.P IS 42. IF THE DIFFERENCE BETWEEN THE 6TH AND 3RD TERM IS 12, FIND THE: COMMON DIFFERENCE, 1ST TERM, 20TH TERM.
  5. MATH!!!! SEQUENCES!!!

    Find out a formula for the Nth term of each of the following sequences. (i)4 7 10 13 16 (ii)1 3 5 7 9 (iii)20 17 14 11 8 (iv)1 4 9 16 25 (v)2 8 18 32 50
  6. Math

    1.) What is the formula for the nth term of the arithmetic sequence that has a common difference of 8 and a first term of 4?
  7. Urgent math

    how do I do this can any body show me how?
  8. Maths: Sequences need help

    The nth term of a sequences of v1,v2,v3 is given by Vn=6 2^n (1):show that for all value of n>1 Vn1=2(Vn-3)?
  9. Maths

    The first 5 terms of an arithmetic sequence are: 7 13 19 25 31 Prove that the difference between the squares of any two terms of the sequence is always a multiple of 24 Nth term = ?
  10. Math

    These are the first 5 terms of a quadratic sequence: 1 3 7 13 21 1st difference: 2 4 6 8 2nd difference: 2 2 2 1n^2: 1 4 9 16 25 adjustment: ?

More Similar Questions