Gregg subtracted some number x from 47, then multiplied the result by two, subtracted 15 and got 45. What was Gregg's number?
1 answer:
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You can factor the 32 out of the sum:
We can also change the index as follows
Now, we have a theorem that states that the series
converges if and only if , and in this case we have
This is your case, because you have
which implies that your series converges, and the value is
