where the initial conditions are such that the denominator never vanishes for any n.
First-order rational difference equationedit
A first-order rational difference equation is a nonlinear difference equation of the form
When and the initial condition are real numbers, this difference equation is called a Riccati difference equation.[3]
Such an equation can be solved by writing as a nonlinear transformation of another variable which itself evolves linearly. Then standard methods can be used to solve the linear difference equation in .
Equations of this form arise from the infinite resistor ladder problem.[5][6]
Solving a first-order equationedit
First approachedit
One approach[7] to developing the transformed variable , when , is to write
where and and where .
Further writing can be shown to yield
Second approachedit
This approach[8] gives a first-order difference equation for instead of a second-order one, for the case in which is non-negative. Write implying , where is given by and where . Then it can be shown that evolves according to
which can arise in some discrete-timeoptimal control problems, can be solved using the second approach above if the matrix C has only one more row than column.
^Camouzis, Elias; Ladas, G. (November 16, 2007). Dynamics of Third-Order Rational Difference Equations with Open Problems and Conjectures. CRC Press. ISBN 9781584887669 – via Google Books.
^ abKulenovic, Mustafa R. S.; Ladas, G. (July 30, 2001). Dynamics of Second Order Rational Difference Equations: With Open Problems and Conjectures. CRC Press. ISBN 9781420035384 – via Google Books.
^Newth, Gerald, "World order from chaotic beginnings", Mathematical Gazette 88, March 2004, 39-45 gives a trigonometric approach.
^"Equivalent resistance in ladder circuit". Stack Exchange. Retrieved 21 February 2022.
^"Thinking Recursively: How to Crack the Infinite Resistor Ladder Puzzle!". Youtube. Retrieved 21 February 2022.
^Brand, Louis, "A sequence defined by a difference equation," American Mathematical Monthly62, September 1955, 489–492. online
^Martin, C. F., and Ammar, G., "The geometry of the matrix Riccati equation and associated eigenvalue method," in Bittani, Laub, and Willems (eds.), The Riccati Equation, Springer-Verlag, 1991.
^Balvers, Ronald J., and Mitchell, Douglas W., "Reducing the dimensionality of linear quadratic control problems," Journal of Economic Dynamics and Control 31, 2007, 141–159.
Further readingedit
Simons, Stuart, "A non-linear difference equation," Mathematical Gazette 93, November 2009, 500–504.