I need a little help with differentials

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    Differentials
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Discussion Overview

The discussion centers around the topic of differential equations, specifically the prerequisites for solving them and the complexity involved in different types of differential equations. Participants explore the foundational knowledge required and the methods used to approach these equations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant emphasizes the need for knowledge of integration before attempting to solve differential equations, as it involves "undoing" derivatives.
  • Another participant suggests specific differential equations to solve, indicating that exponential functions can be solutions under certain conditions.
  • A later reply notes the varying complexity of differential equations, mentioning that some can be solved with simple substitutions while others may require advanced techniques like integral transforms.
  • It is pointed out that many non-linear differential equations cannot be solved with current techniques and may require computational assistance and a deeper understanding of the underlying theory.
  • Participants discuss the importance of mastering basic differentiation rules, such as the chain rule and product rule, as foundational knowledge for tackling differential equations.

Areas of Agreement / Disagreement

Participants generally agree on the necessity of integration knowledge for solving differential equations, but there is no consensus on the methods or complexity of different types of equations, indicating multiple competing views on how to approach the topic.

Contextual Notes

The discussion highlights limitations in solving certain types of differential equations, particularly non-linear ones, and the dependence on various mathematical techniques and computational tools. There is also an acknowledgment that not all differential equations can be approached in the same manner.

James2
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Alright, I know my algebra, geometry, and plane trigonometry. I've been calculating derivatives for a while now, but I wish to get to a higher level of differentiation. Say, differential equations. Could somebody explain how to solve a differential equation?
 
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Welcome to PF!

Hi James2! Welcome to PF! :smile:
James2 said:
Alright, I know my algebra, geometry, and plane trigonometry.

Sorry, but you need to know integration before you can solve differential equations. :redface:

(basically, because you have to "undo" the equation, and "undoing" a derivative is integration)
 
here's some you can do:solve y' - cy = 0. If you have been differentiating much you know that e^ct works.So here is another similar one:

solve y'' - 3y' + 2y = 0.

to solve it just guess the solution to be e^ct, and differentiate to find c.

You will see that e^ct works if and only if c solves the polynomial equation

x^2 -3x + 2 = 0, i.e. if and only if c = 1,2.what about y'' + y' -2y = 0?
 
James2 said:
Alright, I know my algebra, geometry, and plane trigonometry. I've been calculating derivatives for a while now, but I wish to get to a higher level of differentiation. Say, differential equations. Could somebody explain how to solve a differential equation?

Hey James2 and welcome to the forums.

This question that is seemingly so simple, is actually not an easy one to answer.

The thing is that not all differential equations were created equal.

In some cases you can use some rather simple substitutions or calculus identities (like the chain rule) to get the answer and for others, you have to resort to things like integral transforms like the Laplace transform.

Even then with the mathematical machinery that we have, many differential equations like non-linear ones just can't be solved with the techniques we have at the moment and because of this we need to not only use computers, but we have to understand the theory that makes getting a solution actually work to begin with.

So keep the above in mind: in other words, we can't always solve a DE like we solve say a set of equations like x + 2y = 4 and x + 3y = 7 where we get x = blah and y = blah: it's not that easy when you start getting to the complicated kind of equations.

In terms of understanding differentiation though, once you understand all the basics like the chain rule, product rule, quotient rule and others including partial derivatives, then the rest is pretty much using these rules in a given context.
 

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