Let f (x) = (x -arctanx) /(x ^3 )for each x ≠ 0 Find the power series with sum equal to f (x) (when | x | ≤ 1, x ≠ 0), and use this power series to calculate the limit limx → 0f (x).
Yes i did, i got series (-1)^(n+1) *x^(2n-2) (series from n=1 to infinity)
But it was not the correct answer
The correctly answer is ∑k=0∞((−1)^k)/(2k+3)*x^(2k)
I do not understand how he get this answer. Have you any suggestion?