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Q: Find the Laurent series of 1/(z(1-z)) valid for 0<|z|<1. 1/(z(1-z)) = (1/z)(1/(1-z)) = (1/z)Σzⁿ = Σzⁿ⁻¹. = 1/z + 1 + z + z² + ... (n from -1!). Principal part: 1/z (pole of order 1!). Annulus: 0<|z|<1 (punctured disk!)!