Razem, I had some problems going further with this as I've been away from it for some time but I do know the route if I had to solve it: Open the book to the first page of that chapter on power series, start reading, do all of the examples, do a few problems in each section, let it simmer over several days, maybe I don't know about 5-10 problems in all. Eventually, I'd get to the point where I could then go back to this problem and work it. That's really in my opinion how to successfully approach a problem you can't solve in math and elsewhere: put it on the back-burner and work some simpler ones first and then "scale-up"
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