SOLUTION: For the sequence 2,-2,4,-6,10.... find the recursive formula Thank you

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Question 1193479: For the sequence 2,-2,4,-6,10.... find the recursive formula

Thank you
Found 3 solutions by Edwin McCravy, ikleyn, greenestamps:
Answer by Edwin McCravy(20056)   (Show Source): You can put this solution on YOUR website!
She's right. I wasn't thinking.
Answer by ikleyn(52790)   (Show Source): You can put this solution on YOUR website!
.

Edwin created the formula


     = ,   =  = 2


and claimed it as a final formula.



But this formula is incorrect, as everybody can make sure, who will try to use it.



    There are two errors in his formula.

    One error is in indexes. The other error is in signs of addends.



The correct formula is

     = ,   = 2,  = -2,  n = 1, 2, 3, 4, . . . 


Vertical lines |a| at the number "a" mean "absolute value".

Solved.



Answer by greenestamps(13200)   (Show Source): You can put this solution on YOUR website!


The recursive formulas from the other two tutors are very interesting....

But there is a much simpler one.

a(n)=a(n-2)-a(n-1):

4 = 2-(-2)
-6 = -2-4
10 = 4-(-6)
...
etc.
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