Math Problem Statement

What is the range of f(x)=x-5 over x+2

Solution

To determine the range of the function f(x)=x5x+2f(x) = \frac{x-5}{x+2}, we analyze the function thoroughly. Here's a step-by-step breakdown:


1. Understanding the Function

The function f(x)=x5x+2f(x) = \frac{x-5}{x+2} is a rational function, where both the numerator and denominator are linear polynomials.

  • The denominator x+2x+2 cannot be zero. Thus, x2x \neq -2.

2. Horizontal Asymptote (Behavior as xx \to \infty or xx \to -\infty)

When the degree of the numerator and denominator is the same (as in this case), the horizontal asymptote is given by the ratio of the leading coefficients.

  • In f(x)=x5x+2f(x) = \frac{x-5}{x+2}, the leading coefficient of xx in both the numerator and denominator is 1.
    Thus, as xx \to \infty or xx \to -\infty, f(x)1f(x) \to 1.

So, there is a horizontal asymptote at y=1y = 1.


3. Range of the Function

The horizontal asymptote at y=1y = 1 tells us that the function approaches but never equals 11. This suggests that y=1y = 1 is excluded from the range.

To confirm this, we solve for xx in terms of yy to find the set of all possible yy-values:

y=x5x+2.y = \frac{x-5}{x+2}.

Multiply through by x+2x+2 (assuming x2x \neq -2):

y(x+2)=x5.y(x+2) = x-5.

Expand and isolate xx:

yx+2y=x5.yx + 2y = x - 5.

Rearranging terms to isolate xx-terms on one side:

yxx=2y5.yx - x = -2y - 5.

Factor out xx on the left:

x(y1)=2y5.x(y-1) = -2y - 5.

Solve for xx:

x=2y5y1,where y1.x = \frac{-2y - 5}{y - 1}, \quad \text{where } y \neq 1.

The expression for xx is defined for all y1y \neq 1. Therefore, the range of f(x)f(x) is:

(,1)(1,).\boxed{(-\infty, 1) \cup (1, \infty)}.


Final Answer:

The range of f(x)=x5x+2f(x) = \frac{x-5}{x+2} is all real numbers except y=1y = 1, or:

(,1)(1,).\boxed{(-\infty, 1) \cup (1, \infty)}.


Clarification:

  • The function never takes the value y=1y = 1 due to the horizontal asymptote.
  • The rest of the real numbers are part of the range.

Would you like further clarification or a graph of the function for better understanding? Let me know!


Related Questions:

  1. What is the domain of f(x)=x5x+2f(x) = \frac{x-5}{x+2}?
  2. How do you find vertical asymptotes of f(x)=x5x+2f(x) = \frac{x-5}{x+2}?
  3. What happens when x2x \to -2 in f(x)=x5x+2f(x) = \frac{x-5}{x+2}?
  4. How can we graph f(x)=x5x+2f(x) = \frac{x-5}{x+2} and determine its behavior?
  5. What is the range of f(x)=ax+bcx+df(x) = \frac{ax+b}{cx+d} in general?

Tip:

To determine the range of a rational function, solve for xx in terms of yy and check for values of yy that make xx undefined.

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Math Problem Analysis

Mathematical Concepts

Rational Functions
Domain and Range
Horizontal Asymptotes

Formulas

f(x) = (x - 5) / (x + 2)
y = (x - 5) / (x + 2) → x = (-2y - 5) / (y - 1)

Theorems

Horizontal asymptote rule: For rational functions where the degrees of numerator and denominator are equal, the asymptote is the ratio of leading coefficients.

Suitable Grade Level

Grades 10-12