Thursday

April 17, 2014

April 17, 2014

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

+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 10:27amhelp 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.

**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...

math - Write an equation for nth term in the sequence: -2, 5, -10, 17, -26

MATH PLS HELp - Write an equation for nth term in the sequence: -2, 5, -10, 17...

MATH!!!! SEQUENCES!!! - Find out a formula for the Nth term of each of the ...

math - The third and seventh terms of an arithmetic sequence are 10 and 20. 1) ...

arithmetic - THE SUM OF THE 2ND AND 5TH TERMS OF AN A.P IS 42. IF THE DIFFERENCE...

FUNCTIONS 11 - Write an equation for nth term in the sequence: -2, 5, -10, 17, -...

math - what are the similarities and differences between an arithmetic sequence ...

Maths - Hi, I am working on some Nth problems - can anyone tell me if this is ...