Solution

ID: past-exam-of-the-mathematics-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2012/paper-1/19/a/iv/solution

Insert into the exponential series . For every fixed , this gives the expansion with absolute convergence
This is a Laurent series in inverse powers of , as requested. It is not a Maclaurin series about zero: that series has every coefficient zero and cannot equal on a punctured neighborhood of zero. There is no contradiction, since the inverse-power expansion does not apply at .

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