How Do You Solve Yp for the ODE y'' - 3y' - 10y = exp(x)?

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Discussion Overview

The discussion revolves around finding the particular solution \( Y_p \) for the ordinary differential equation (ODE) \( y'' - 3y' - 10y = \exp(x) \). Participants explore methods for solving this ODE, including the guessing method and considerations related to the characteristic equation.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant initially seeks help to find \( Y_p \) for the given ODE, stating the homogeneous solution \( Y_h = c_1 \exp(-5x) + c_2 \exp(2x) \).
  • Another participant expresses frustration over not being able to solve the problem during a midterm exam and seeks the answer afterward.
  • A participant mentions a previous simpler case with \( \exp(1) \) and contrasts it with the current problem involving \( \exp(x) \), indicating increased difficulty.
  • There is a discussion about the characteristic equation, with one participant confirming the calculation of the discriminant as \( \sqrt{49} = 7 \).
  • A later reply claims to have found the particular solution using the guessing method, proposing \( Y_p = -\exp(x)/12 \). However, this solution is not universally accepted as correct.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the method for finding \( Y_p \) or the correctness of the proposed solutions. Multiple competing views and methods remain present in the discussion.

Contextual Notes

Some participants express uncertainty about the guessing method and its applicability, particularly in relation to the form of the non-homogeneous term \( \exp(x) \). There are also indications of confusion regarding basic concepts after time away from academic study.

final_d3stinati
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Edit: SOLVED!
**********************
Please help me find Yparticular for this ODE:

y''-3y'-10y=exp(x)
...
m^2-3*m-10=0 -> Yh = c1*exp(-5x)+c2*exp(2x)
Yp = ?

Thank you!
 
Last edited:
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This was a question in my midterm exam which I coudn't figure out. My midterm is over now! I just want to find the answer :confused:
 
final_d3stinati said:
Please help me find Yparticular for this ODE:

y''-3y'-10y=exp(x)
...
m^2-3*m-10=0 -> Yh = c1*exp(-5x)+c2*exp(2x)
Yp = ?

Thank you!


Aww you changed it to exp(x)
:devil:
 
sorry! I mistyped.. in case of exp(1), it was very easy! Yh=-exp(1)/10
exp(x) makes it really hard for me! I can't use Guessing mehtod or even Wronskian!
 
no!
sqrt(3^2-4(-10))=sqrt(49)=7
 
final_d3stinati said:
no!
sqrt(3^2-4(-10))=sqrt(49)=7

:eek:

true true :biggrin:


see what happens when you are a year out of college you forget basic stuff :frown:
 
Oops!
It was very easy! I got it.
Guessing Method:
Yp= k*exp(x) ---> Yp=-exp(x)/12
 

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