Q. 5. Tentukan jari-jari konvergen deret berikut dengan cara formula Cauchy Hadamard: (bobot 20)n=2∑∞(n−2)3n(z)nSELAMAT MENGERJAKAN =
Write Cauchy-Hadamard formula: Write down the Cauchy-Hadamard formula.The radius of convergence R is given by L1, where L is the limit superior of the nth root of the absolute value of the nth term.
Identify nth term: Identify the nth term of the series.The nth term is an=(n−2)zn3n.
Calculate nth root: Calculate the nth root of the absolute value of the nth term.We take the nth root of ∣an∣ which is ∣∣(n−2)zn3n∣∣n1.
Simplify expression: Simplify the expression.The nth root of ∣an∣ becomes ∣z3∣⋅∣(n−2)n11∣.
Find limit: Find the limit as n approaches infinity. The limit of ∣(n−2)n11∣ as n approaches infinity is 1, so L=∣z3∣.
Calculate radius: Calculate the radius of convergence.The radius of convergence R is L1, so R=∣z3∣1=3∣z∣.
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