Posted by **Samantha** on Friday, February 4, 2011 at 12:00am.

If f(x)= 3/x-4 and g(x)=2x, there is at least one value of x for which the composite function f(g(x)) cannot be evaluated.

What is that value of x? For what value(s) of x is it impossible to evaluate g(f(x))?

How do you figure this out?

- Math -
**MathMate**, Friday, February 4, 2011 at 6:36am
As a first step, graph f(x) and find the discontinuity for the function f(x).

Call this point x0.

If this point x0 is found, x0=g(x) is not admissible in the composition f(g(x)), because x0 is not in the domain of f(x).

Since x0=g(x)=2x, we conclude that x=x0/2 is not an admissible value of x in f(g(x)) because

f(g(x0/2)) = f(2(x0/2))=f(x0) which is undefined.

You can find the value of x in the second part using a similar argument.

If you need further help, please post.

## Answer this Question

## Related Questions

- ALGEBRA - Match the function f ( x ) evaluated at each value of x to the correct...
- Math - is x=5 a function No. The plot (graph) is a vertical line at x=5, so y ...
- ALGEBRA - wo quadratic functions are shown. Function 1: f(x) = 4x2 + 8x + 1 ...
- Algebra 1 - Which statement is always a correct conclusion about the values x ...
- calculus - Suppose that f(x)= square root of x and g(x)= 3x-4 and you are asked ...
- Math - I posted this question before but accidentally typed in the wrong values...
- Math Help! - A.) Determine "a" and "k" so both points are on the graph of the ...
- trig - For the function -2sin(x-(pi/3)) between x = 0 and x = 2 : (6 marks) For ...
- math - The application of one function followed by the application of a second ...
- math - What is the number? It has seven digits. The value of one of its digits ...

More Related Questions