(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

5^2 - 5^3 + 5^4 - ... + (-1)^k*5^k whre k is an integer with k >= 2

2. Relevant equations

3. The attempt at a solution

I know (5^(k-1) - 5^2)/2 gives you the sum if they were all positive. I tried multiplying it by (-1)^k or something but that just changes the sign. I wish I could give you more but I can't.

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# Sum of Getometric Sequence with alternating signs

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