There was one example in my school work today that didn't make sense.

You need to figure out the formula for the following pattern

-1, 5, -9, 13, -7


The provided solution is:

Odd numbers: -1^n

Even numbers: 4n -3


They don't show how they got there at all.


As you could probably see the odd number solution does not work.

But I can't figure out the actual formula.

Could someone please help me with this?

 Mar 5, 2018
edited by Guest  Mar 5, 2018

The formula is a combination of both ie (-1)n (4n-3)  where n = 1,2,3,....


you see the (-1)is just the mathematical way of putting a minus sign in front of a number.


odd powers give a minus and even powers give a plus eg (-1)= -1 ,  (-1)= 1


and of course the 4n-3 gives you  1,5,9,......

 Mar 6, 2018

Your suggestion will work only if the 5th term (-7) is wrong, which is quite likely because -17, which will work, is very close to -7 that he/she has written down.

 Mar 6, 2018

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