Solving for y: Why/How do y and e^x switch places?

In summary, the problem involves solving for y in an equation with natural logarithms. The solution involves exponentiating to get rid of the ln and then using algebra to rearrange the equation in terms of y. This may involve switching the positions of y and e^x. The graphs of the original equation and the rearranged equation may have symmetry over the line y=x.
  • #1
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Homework Statement



Doing a DE and need to solve for y, just wondering about this particular case.

Homework Equations



ln ((2y-1)/(y-1)) = x for y

The Attempt at a Solution



Wolfram says the result is: http://www.wolframalpha.com/input/?i=solve+ln+((2y-1)/(y-1))+=+x+for+y"

How/why did the y and e^x switch places? I know the first step is to exponentiate to get rid of the ln yielding (2y-1)/(y-1) = e^x, but why the heck would you just switch the y's with the e^x after that? Is it because the graph has symmetry over the y=x line? That's all I can figure. If that is the case, how can you tell this is true offhand?

http://www.wolframalpha.com/input/?i=graph+y+=+(e^x-1)/(e^x-2)"

http://www.wolframalpha.com/input/?i=graph+(2y-1)/(y-1)+=+e^x"

Thanks!
 
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  • #2
so what exactly is the equation? i don't get what you are trying to say. is this about Inverse Function or Logarithm?(log and ln?)
 
  • #3
The equation is in terms of x, I want it in terms of y. I want y = " ". Wolfram did this for me, but I'm wondering HOW it did it. It switched the y's with the e^x, and it looks like it came out right, what method/identity did it use to achieve this?
 
  • #4
It's just algebra, multiply both sides by y-1, gather like terms, factor out the y, etc.
 

Related to Solving for y: Why/How do y and e^x switch places?

1. Why do y and e^x switch places when solving for y?

When solving for y, we are trying to isolate the dependent variable y on one side of the equation. In this case, e^x is the independent variable and y is the dependent variable. So, by switching their places, we can easily solve for y and express it in terms of e^x.

2. How do we know when to switch y and e^x when solving for y?

In most cases, we switch y and e^x when we have an equation in the form of y = f(x), where f(x) is some function of x. This allows us to easily solve for y by isolating it on one side of the equation.

3. Can we switch y and e^x for any equation when solving for y?

No, we cannot switch y and e^x for any equation. This method only works for equations where y is the dependent variable and e^x is the independent variable. If we switch them for other types of equations, we may not get the correct solution for y.

4. Are there any other variables that can switch places with y when solving for y?

Yes, there are other variables that can switch places with y when solving for y. For example, if we have an equation in the form of y = f(z), we can switch y and z to solve for y. The key is to identify the dependent variable and switch it with the independent variable.

5. Is there a specific reason why y and e^x are the most common variables to switch when solving for y?

Yes, there is a specific reason why y and e^x are the most common variables to switch when solving for y. This is because e^x is the natural exponential function, and it appears frequently in many mathematical models and equations. Therefore, it is often used as the independent variable in equations involving exponential functions.

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