- #1

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## Homework Statement

This is a question about one single step of a solution of a long equation.

http://www.geocities.com/link_herooftime/math.jpg

where P, U and V are variables. a, b, c, d are constants and t is the time, which are measured in discrete periods.

The question is how to go from equation 1 to equation 3, and how the L appears.

**Attempted solution**

I have solved it until equation 2, and I see that the solution requires the extraction of P out of the bracket on the left hand side. Problem becomes how to do it, since the P minus one period doesn't equal P of current period. Nevertheless the key somehow does this. Does this require some other method than simple algebra?

The key mentions it is a "stochastic difference equation".