How to Get Rid of Natural Logarithms in Separable Differential Equations

In summary, the conversation is about solving a differential equation and getting stuck at a certain point. The student describes their process of factoring and manipulating the equation, leading to a final equation with logarithms. They mention wanting to get rid of the logarithms and ask for help.
  • #1
Aerosion
53
0

Homework Statement



so here's my equation:

dy/dx=(xy+3x-y-3)/(xy-2x+4y-8)

so what i did first was factor out the right side

=(x+1)(y-3)/(x+4)(y-2)

then i did a bunch of manipulation to get the ys on one side and the xs on another (i won't write this out right now but if anyone wants me to i can)

and got

(y-2)/(y+3) dy = (x-1)/(x+4) dx

of course i integrate, i get

y-5*ln(y+3) = x-5ln(x+4)

i want to get rid of the lns, right? so i multiplied them by e (like e^(ln(y+3)

then i got -4y-15=-4x-20

i'm not sure what to do after this because i looked at the answer at the back of my book and it said something completely different to what I've done so far, any help?



Homework Equations





The Attempt at a Solution

 
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  • #2
Shouldn't your exponent for [itex]e[/itex] be the entire expression on each side of the equation?

i.e.

[tex] e^{y-5ln(y+3)}=e^{x-5ln(x+4)}[/tex]
 

1. What is separation of variables?

Separation of variables is a mathematical technique used to solve certain types of differential equations. It involves separating a multivariable function into simpler functions in order to solve for each variable individually.

2. When is separation of variables used?

Separation of variables is typically used when solving partial differential equations, which involve multiple independent variables. It can also be used to solve certain types of ordinary differential equations.

3. What are the steps for using separation of variables?

The first step is to identify the variables in the equation and determine if they are separable. Then, the equation is manipulated to separate the variables on opposite sides of the equals sign. Next, each side is integrated with respect to its respective variable. Finally, the resulting equations are solved for each variable.

4. What are the limitations of separation of variables?

Separation of variables can only be used for certain types of differential equations, such as those that are linear and homogeneous. It also requires the variables to be separable, which may not always be the case. Additionally, it may not provide a complete solution to the original equation.

5. Are there any applications of separation of variables in science?

Yes, separation of variables is commonly used in various fields of science, such as physics, engineering, and mathematics. It can be used to model physical systems and phenomena, such as heat transfer, fluid dynamics, and wave propagation.

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