Not able to solve

please give me an approach to solve this problem
i tried
1.summing all values from m to n
i think we have to calculate sum till nth term and subract sum till m-1th term
tellme an approach please

I will recommend you to first solve this question and then do version II.
You will know a lot of things.

I have already done basic problems on matrix exponentiation and this problem also.In fibosum we were able to derive a simple formula but cannot do that for this case

Yes your approach is correct, you have to find sum till nth and then subtract (m-1)th from that.

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