Inverse Function Homework: Find f(x) = x + 4/x

In summary, to find the inverse function for f(x) = x + 4/x, you can solve for x by treating the equation as a quadratic equation or combining the fractions on the right side into a single fraction and cross-multiplying. This will result in an equation of the form ax^2 + bx + c = 0, which will give the inverse function.
  • #1
elitewarr
63
0

Homework Statement


Find the inverse function for f(x) = x + 4/x


Homework Equations





The Attempt at a Solution


I tried many times but just can't get the answer.
Is there any trick to this question?

Thank you
 
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  • #2
Basically, what you want to do, is solve
y = 4x + 4/x
for x.
Secretly, you can view this as a quadratic equation. You can either multiply through by x, then this becomes immediately apparent.

If you're looking for a more general approach, I suggest combining the two fractions (4x/1 and 4/x) on the right hand side into a single fraction A/B, then you can cross-multiply (y = A/B becomes yB = A).

In both cases, you can get an equation of the form
ax2 + bx + c = 0
the solution(s) of which give an inverse function.
 
  • #3
Ahh! Why didn't I think of that. Thanks!
 

FAQ: Inverse Function Homework: Find f(x) = x + 4/x

What is an inverse function?

An inverse function is a mathematical operation that undoes the original function. In other words, if a function f(x) maps an input to an output, the inverse function will map the output back to the original input.

How do I find the inverse function of f(x) = x + 4/x?

To find the inverse function, we first need to switch the positions of x and y in the original equation. This gives us x = y + 4/y. Next, we solve for y by multiplying both sides by y, giving us xy = y^2 + 4. Rearranging this equation to the form y^2 - xy + 4 = 0, we can then use the quadratic formula to solve for y in terms of x.

Can the inverse function of f(x) = x + 4/x be written as a single equation?

Yes, the inverse function can be written as f^-1(x) = (x + √(x^2 - 16)) / 2. This is derived from the quadratic formula solution for y in the previous step.

How do I check if my inverse function is correct?

To check if your inverse function is correct, you can use the composition method. This means plugging the inverse function into the original function and vice versa, and making sure that the resulting equation simplifies to just x. If it does, then you have found the correct inverse function.

Is there more than one inverse function for f(x) = x + 4/x?

Yes, there are two possible inverse functions for this equation. This is because the original function is not one-to-one, meaning there are multiple inputs that can result in the same output. Therefore, there are two possible ways to map the output back to the original input, resulting in two different inverse functions.

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