Difference between revisions of "Associated Laguerre L"

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Let $\lambda \in \mathbb{R}$. The associated Laguerre polynomials, $L_n^{(\lambda)}(x)$ are solutions of the differential equation
 
Let $\lambda \in \mathbb{R}$. The associated Laguerre polynomials, $L_n^{(\lambda)}(x)$ are solutions of the differential equation
 
$$x\dfrac{d^2y}{dx^2} + (\lambda+1-x)\dfrac{dy}{dx} + ny=0.$$
 
$$x\dfrac{d^2y}{dx^2} + (\lambda+1-x)\dfrac{dy}{dx} + ny=0.$$
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\end{array}$$
 
\end{array}$$
  
[[File:Associatedlaguerrealpha=1.png|500px]]
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File:Associatedlaguerrealpha=1.png|Graph of $L_n^{(1)}$ on $[-2,10]$.
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=Properties=
 
=Properties=
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<strong>Theorem:</strong> The following formula holds:
 
$$L_n^{(\lambda)}(x) = \displaystyle\sum_{k=0}^n (-1)^k {n+\lambda \choose n-k} \dfrac{x^k}{k!}.$$
 
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<strong>Proof:</strong> █
 
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=See also=
<strong>Theorem:</strong> The following formula holds:
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[[Laguerre L]]<br />
$$L_n^{(\lambda+\beta+1)}(x+y) = \displaystyle\sum_{k=0}^n L_k^{(\lambda)}(x)L_{n-k}^{(\beta)}(x).$$
 
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<strong>Proof:</strong> █
 
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<strong>Theorem:</strong> The following formula holds:
 
$$L_n^{(\lambda)}(x) = L_n^{(\lambda+1)}(x)-L_{n-1}^{(\lambda+1)}(x).$$
 
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<strong>Proof:</strong> █
 
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=References=
<strong>Theorem:</strong> The following formula holds:
 
$$nL_n^{(\lambda+1)}(x) = (n-x)L_{n-1}^{(\lambda+1)}(x)-(n+\lambda)L_{n-1}^{(\lambda)}(x).$$
 
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<strong>Proof:</strong> █
 
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{{:Orthogonal polynomials footer}}
<strong>Theorem:</strong> The following formula holds:
 
$$xL_n^{(\lambda+1)}(x)= (n+\lambda)L_{n-1}^{(\lambda)}(x)-(n-x)L_n^{(\lambda)}(x).$$
 
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<strong>Proof:</strong> █
 
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[[Category:SpecialFunction]]
<strong>Theorem:</strong> The following formula holds:
 
$$\dfrac{d^k}{dx^k} L_n^{(\lambda)}(x) = (-1)^kL_{n-k}^{(\lambda+k)}(x).$$
 
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<strong>Proof:</strong> █
 
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Latest revision as of 13:38, 15 March 2018

Let $\lambda \in \mathbb{R}$. The associated Laguerre polynomials, $L_n^{(\lambda)}(x)$ are solutions of the differential equation $$x\dfrac{d^2y}{dx^2} + (\lambda+1-x)\dfrac{dy}{dx} + ny=0.$$

The first few Laguerre polynomials are given by $$\begin{array}{ll} L_0^{(\lambda)}(x) &= 1 \\ L_1^{(\lambda)}(x) &= -x+\lambda+1 \\ L_2^{(\lambda)}(x) &= \dfrac{x^2}{2} -(\lambda+2)x+\dfrac{(\lambda+2)(\lambda+1)}{2} \\ L_3^{(\lambda)}(x) &= -\dfrac{x^3}{6} + \dfrac{(\lambda+3)x^2}{2} - \dfrac{(\lambda+2)(\lambda+3)x}{2} + \dfrac{(\lambda+1)(\lambda+2)(\lambda+3)}{6} \\ \vdots \end{array}$$

Properties

See also

Laguerre L

References

Orthogonal polynomials