Thursday
May 5, 2016

# Homework Help: math

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

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

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.

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