Excess Kurtosis of Pareto Distribution/Lemma 4
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Lemma for Excess Kurtosis of Pareto Distribution
- $3 a^3 \paren {a - 2}^2 \paren {a - 3} \paren {a - 4} = 3 a^7 - 33 a^6 + 132 a^5 - 228 a^4 + 144 a^3$
Proof
\(\ds 3 a^3 \paren {a - 2}^2 \paren {a - 3} \paren {a - 4}\) | \(=\) | \(\ds 3 a^3 \paren {a^2 - 4 a + 4} \paren {a^2 - 7 a + 12}\) | ||||||||||||
\(\ds \) | \(=\) | \(\ds \paren {3 a^5 - 12 a^4 + 12 a^3} \paren {a^2 - 7 a + 12}\) | ||||||||||||
\(\ds \) | \(=\) | \(\ds 3 a^7 + \paren {-21 - 12} a^6 + \paren {36 + 84 + 12} a^5 + \paren {-144 - 84} a^4 + 144 a^3\) | ||||||||||||
\(\ds \) | \(=\) | \(\ds 3 a^7 - 33 a^6 + 132 a^5 - 228 a^4 + 144 a^3\) |
$\blacksquare$