Solve Inverse Function of g(x)=(x2/e)+2 ln(x)-e

In summary, to evaluate g-1(2), one can plug in x=e into the original function to get (e,2) and then swap the x and y values to get (2,e). Therefore, the evaluation of g-1(2) is e. This can be found by recognizing the 2 in front of ln(x) in the original function and using the fact that ln(e) = 1.
  • #1
raptik
21
0

Homework Statement


The function g(x) = (x2/e) + 2 ln(x) - e on (0,infinity) is one-to-one. Evaluate g-1(2)

Homework Equations


Find x in terms of y. Then switch x and y. Plug in 2 to the new equation.

The Attempt at a Solution


I can think of no way to get x explicitly in terms of y. I considered plugging in 2 to the original equation to get (x1,y1) and switching the two, but without a calculator, it seems unlikely to find a straightforward answer. Please help.
 
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  • #2
The question only ask you to evaluate [itex] g^{-1}(2)[/itex] it did not ask for a formula.

Think about what an inverse is if f(x) =y then [itex] f^{-1} (y) = ? [/itex].

Inverse "brings things back". If I throw a ball at you and "inverse" is you throwing the same ball at me, right ?
 
  • #3
The answer choices are: A) 1 B) 2 C) e D) e2 E) 0

One of these is the correct "evaluation".

I follow that if f(x) =y then f-1 (y) = x

But when I don't know how to get to x, I'm not going to be able to solve this.
 
  • #4
Have you considered finding g(e) ?
 
  • #5
╔(σ_σ)╝ said:
Have you considered finding g(e) ?

Oh!

If I put x=e, then I get g(e) = 2. So (e,2). Then it's inverse is (2,e) which matches with g-1(2) to give me e. I see how that could work, but how did you have the intuition to add e to the original problem? I suppose it's a matter of plugging something that seems like it would give me the required value until it works. Thnx for help.
 
  • #6
raptik said:
Oh!

If I put x=e, then I get g(e) = 2. So (e,2). Then it's inverse is (2,e) which matches with g-1(2) to give me e. I see how that could work, but how did you have the intuition to add e to the original problem? I suppose it's a matter of plugging something that seems like it would give me the required value until it works. Thnx for help.
When i looked at g i knew that the x^2 term would cause problems. I looked again at g and realized there was a 2 infront of lnx and i knew ln(e) =1. From there i realized that if i found g(e) i would get 2. ;-)
 

Related to Solve Inverse Function of g(x)=(x2/e)+2 ln(x)-e

What is an inverse function?

An inverse function is a function that "undoes" the original function. In other words, if we plug in the output of the original function into the inverse function, we will get back the input of the original function.

How do you solve for the inverse function of a given function?

To solve for the inverse function, we can follow these steps:

  1. Replace f(x) with y.
  2. Swap the x and y variables.
  3. Solve for y.
  4. Replace y with f-1(x).

What is the inverse function of g(x) = (x2/e) + 2ln(x) - e?

The inverse function of g(x) is f-1(x) = ex - 2ln(x) + e.

How do you check if a function is its own inverse?

To check if a function is its own inverse, we can plug in the function into itself and see if we get back the original input. In other words, if f(f(x)) = x, then the function is its own inverse.

What is the domain and range of the inverse function of g(x) = (x2/e) + 2ln(x) - e?

The domain of the inverse function is the range of the original function, which is (0,∞). The range of the inverse function is the domain of the original function, which is (-∞,∞).

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