- #1

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I think you go about this by factoring 2009 as 7*7*41. I'm pretty much stuck.

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- Thread starter Oster
- Start date

- #1

- 85

- 0

I think you go about this by factoring 2009 as 7*7*41. I'm pretty much stuck.

- #2

Dick

Science Advisor

Homework Helper

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What are the last digits of 2009^1, 2009^2, 2009^3 etc? Keep going until you see the pattern.

- #3

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To simplify dick's post: it suffices to look at 9^1, 9^2, 9^3,..., do you see why?

- #4

Dick

Science Advisor

Homework Helper

- 26,263

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To simplify dick's post: it suffices to look at 9^1, 9^2, 9^3,..., do you see why?

And it's even easier than that if you know mod arithmetic and notice 2009 is equal to (-1) mod 10.

- #5

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- 0

yes thank you, i see the pattern.

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