Solving tricky functional equation

  • Thread starter Frogeyedpeas
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In summary, the conversation discusses a linear functional operator and how to solve an equation involving this operator. It also mentions a specific case for constant functions and how to find the solution using the assumption of a specific form for the function. The conversation ends with a question about solving the equation for more general functions, which is suggested to be done by looking into delay differential equations.
  • #1
Frogeyedpeas
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Consider the following linear functional operator:

$$Q_w[f(x)] = \lim_{h\rightarrow w} \lbrace \frac{f(x + h) - f(x)}{h} \rbrace $$

How does one solve the equation

$$a_0(x)Q_0[f(x)] = a_1(x)Q_1[f(x)]$$

Spelt out that is:

$$a_0(x)*f'(x) = a_1(x)(f(x+1) - f(x))$$

For the case of constant functions $a_0(x) = a_0$ and $a_1(x) = a_1$ the solution is simply found by assuming

$$f(x) =e^{Lx}$$

thereby implying:

$$a_0L e^{Lx} = a_1(e^{Lx}(e^{L} - 1))$$

which can be solved as

$$\frac{L}{1 - e^{L}} = =\frac{a_1}{a_0} $$

And L can be extracted through the use of Lambert-W function.But what about more general functions?
 
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  • #2
This is a delay differential equation, so I'd start looking there. (Not my expertise unfortunately)
 

Related to Solving tricky functional equation

1. What is a functional equation?

A functional equation is an equation that involves functions and requires finding the functional relationships between the variables involved. It is used to describe how one or more variables depend on another variable.

2. Why are functional equations considered tricky?

Functional equations can be tricky because they often involve abstract concepts and require creative thinking to solve. They may also have multiple solutions or no solutions at all, making them challenging to solve.

3. What are some common strategies for solving tricky functional equations?

Some common strategies for solving tricky functional equations include substitution, manipulating the equation algebraically, using special functions or properties, and trial and error. It is also helpful to have a good understanding of the properties and behaviors of different types of functions.

4. Can you give an example of a tricky functional equation and how to solve it?

An example of a tricky functional equation is f(x+y) = f(x) + f(y). To solve this, we can substitute x = 0 and y = 0 to get f(0) = 2f(0). This means that f(0) = 0. Then, we can substitute x = 0 and y = x to get f(x) = f(x) + f(0). Therefore, f(x) = 0 for all x. This is just one of the possible solutions for this equation.

5. How can solving tricky functional equations be applied in real life?

Solving tricky functional equations can be applied in various fields such as physics, engineering, economics, and computer science. For example, functional equations can be used to model real-life situations and make predictions about how certain variables will behave. They can also be used to optimize systems and find the most efficient solutions.

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