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| Question 115576:  I am very frustrated!  I am doing a piece of coursework and have discovered a changing difference pattern. Could someone please explain to me how to apply it and simplify it for my own results. I know the algebraic expression for a changing difference sequence is: a + (n-1)d + half(n-1)(n-2)c
 a = value of first term in sequence
 d = first difference between the first two numbers
 c = is the change between one difference and the next
 a = 481
 d = 600
 c = 240
 Changing Difference Sequence:
 
 481, 1081, 1921, 3001, 4321  Sequence
 600   840   1080  1320    first difference
 240   240   240       Second difference
 I have tried for several hours to figure it out for my own results but have just got frustrated.  I need to solve the nth term formula for this changing difference sequence to move on with my coursework.  Thank you so much for any help!
 
 Found 2 solutions by  stanbon, richwmiller:
 Answer by stanbon(75887)
      (Show Source): 
You can put this solution on YOUR website! a + (n-1)d + half(n-1)(n-2)c a = value of first term in sequence
 d = first difference between the first two numbers
 c = is the change between one difference and the next
 a = 481
 d = 600
 c = 240
 Changing Difference Sequence:
 481, 1081, 1921, 3001, 4321 Sequence
 600 840 1080 1320 first difference
 240 240 240 Second difference
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 changing difference = 481+(5-1)600 + (1/2)(5-1)(5-2)240
 cd = 481 + 2400 + 6*240
 cd = 4321
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 Comment: I've never heard of this "changing difference", but if your
 formulas and numbers are correct 4321 is the result.
 Question: What does cd=4321 tell you?
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 Cheers,
 Stan H.
 
Answer by richwmiller(17219)
      (Show Source): 
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