Determine coefficients of a differential equation

In summary, the conversation discusses a problem involving a system described by a function and the determination of coefficients in another system. The individual has been struggling with the problem for four days and has tried various methods to solve it. Eventually, they are able to solve the problem by equating two equations and finding values for the coefficients.
  • #1
jackonelli
2
0
Hi there.

I've been struggling with this problem for days now (4 days, no joke) and I feel like I have a mental block and really cannot get any further.

I have a system that's described by

[tex] f(t) = g''(t) + 15g'(t) + 1600g(t) [/tex] Where the input is [tex]g(t)[/tex]
The problem is to, with this information, determine the coefficients in another system, where the input is[tex]f(t)[/tex]and the output is given by [tex]u(t)[/tex], so that [tex]u(t) = g(t)[/tex]
This other system is given by
[tex]c_2u''(t)+c_1u'(t)+c_0u(t) = b_2f''(t) + b_1f'(t) + b_0f(t)[/tex]

I think this is supposed to be simple and I think I make it more difficult in my head than it is. I first substituted f(t) in the second differential equation with the left hand side of the first equation:

[tex]c_2u''(t)+c_1u'(t)+c_0u(t) = b_2f''(t) + b_1f'(t) + b_0(g''(t) + 15g'(t) + 1600g(t))[/tex]
[tex]=> c_2u''(t)+c_1u'(t)+c_0u(t) = b_2f''(t) + b_1f'(t) + b_0g''(t) + b_015g'(t) + b_01600g(t)[/tex]I´m supposed to get numerical values for all coefficients but I really can’t figure out what coefficients makes u(x) = g(t). I don't really know how to proceed. I've tried a lot of other ways too, for example solve for u(t) and g(t) explicitly:[tex]u(t) = \frac{b_2}{c_0}f''(t) + \frac{b_1}{c_0}f'(t) + \frac{b_0}{c_0}f(t)-\frac{c_2}{c_0}u''(t)-\frac{c_1}{c_0}u'(t)[/tex] and [tex] g(t) = \frac{1}{1600}g''(t) + \frac{15}{1600}g'(t) -\frac{1}{1600}f(t)[/tex]

And then putting their right hand sides equal each other, but this didn't really get me anywhere.

Just before posting this question I’ve been staring and trying for another 4 hours, and I feel I’m that my self-confidence is at an all-time low and I'm starting to ask myself if I really should be doing math at all (Yes, it's really a first world issue, I know).

REALLY grateful for any help!
 
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  • #2
Ok, sorry. Actually, putting the last two equations equal to each other really does give values to the coefficients. So I think that I managed to solve it after all:smile: This was only a sub-problem, so maybe I'll be back later...
 

What is a differential equation and why do we need to determine its coefficients?

A differential equation is a mathematical equation that describes the relationship between a function and its derivatives. It is used to model many real-world phenomena, such as population growth, chemical reactions, and electrical circuits. Determining the coefficients of a differential equation allows us to solve the equation and make predictions about the behavior of the system it represents.

What are the steps involved in determining the coefficients of a differential equation?

The first step is to identify the order of the differential equation, which is determined by the highest derivative present. Next, we must separate the equation into its individual terms and coefficients. Then, we use algebraic operations and mathematical techniques, such as integration and differentiation, to solve for the coefficients. Finally, we can check our solutions by substituting them back into the original equation.

Can we always determine the coefficients of a differential equation?

No, not all differential equations have solutions that can be expressed in terms of known functions. In some cases, we may only be able to approximate the coefficients using numerical methods. Additionally, there are certain types of differential equations, such as partial differential equations, that require more advanced techniques to determine the coefficients.

How are the coefficients of a differential equation related to its solutions?

The values of the coefficients directly affect the behavior of the solutions to a differential equation. For example, changing the value of a coefficient may cause the solution to oscillate or approach a steady state. The coefficients also determine the stability and convergence of the solutions, which are important factors in understanding the behavior of a system over time.

Are there any applications of determining coefficients of a differential equation?

Yes, there are many practical applications of determining the coefficients of a differential equation. For example, in physics, we can use differential equations to model the motion of objects and determine the forces acting upon them. In economics, differential equations can be used to model financial systems and make predictions about market trends. Additionally, differential equations are often used in engineering to design and optimize systems, such as control systems and circuits.

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