When graphing the function [tex]f(x)=\frac{x^2-81}{x^2-11x+18}[/tex] on your graphing calculator, what is the most appropriate viewing window for determining the domain and range of the function?

A. [tex]X_{\min} = -10, X_{\max} = 10[/tex], [tex]Y_{\min} = -10, Y_{\max} = 10[/tex]
B. [tex]X_{\min} = -5, X_{\max} = 5[/tex], [tex]Y_{\min} = -5, Y_{\max} = 5[/tex]
C. [tex]X_{\min} = 0, X_{\max} = 10[/tex], [tex]Y_{\min} = 0, Y_{\max} = 10[/tex]
D. [tex]X_{\min} = -10, X_{\max} = 0[/tex], [tex]Y_{\min} = -10, Y_{\max} = 0[/tex]



Answer :

To determine the most appropriate viewing window for graphing the function [tex]\( f(x) = \frac{x^2 - 81}{x^2 - 11x + 18} \)[/tex] on your graphing calculator, we need to understand the critical aspects of the function including its asymptotes, holes, and the general behavior of the function.

1. Factorizing the Denominator:
The denominator of our function is [tex]\( x^2 - 11x + 18 \)[/tex]. To find the zeros of the denominator, we can factorize as follows:
[tex]\[ x^2 - 11x + 18 = (x - 2)(x - 9) \][/tex]

2. Holes of the Function:
Zeros of the denominator [tex]\( x = 2 \)[/tex] and [tex]\( x = 9 \)[/tex] would cause the function to be undefined at these points, leading to holes (or removable discontinuities) at these x-values.

3. Examining the Numerator:
The numerator is [tex]\( x^2 - 81 \)[/tex], which can be factorized as:
[tex]\[ x^2 - 81 = (x - 9)(x + 9) \][/tex]
This means the numerator becomes zero at [tex]\( x = 9 \)[/tex] and [tex]\( x = -9 \)[/tex].

4. Simplification and Holes:
Since [tex]\( x = 9 \)[/tex] is a zero of both the numerator and denominator, this point is specifically a hole. The function simplifies to:
[tex]\[ f(x) = \frac{(x + 9)}{(x - 2)} \quad \text{for} \quad x \neq 9 \][/tex]

5. Asymptotes:
The vertical asymptote occurs where the function is undefined, excluding the holes. Therefore, [tex]\( x = 2 \)[/tex] is a vertical asymptote.

6. Behavior Analysis:
- As [tex]\( x \to \infty \)[/tex] and [tex]\( x \to -\infty \)[/tex]: The function approaches the broader behavior of [tex]\( \frac{x^2}{x^2} = 1 \)[/tex] indicating a horizontal asymptote at [tex]\( y = 1 \)[/tex].

Given this analysis, we need a viewing window that includes critical points like [tex]\( x = 2, 9 \)[/tex], and enough space to understand the behavior of the function around these points.

Considering the holes at [tex]\( x = 2 \)[/tex] and [tex]\( x = 9 \)[/tex], a good x-range should include these points and extend beyond to give a clear view of the behavior of the function.

The appropriate window is:
[tex]\[ X \min: -10, X \max: 10 \\ Y \min: -10, Y \max: 10 \][/tex]

This range provides a sufficiently broad view to include the key characteristics of the function, hence:

Answer: [tex]$X$[/tex] min: [tex]$-10$[/tex], [tex]$X$[/tex] max: 10 \\
[tex]$Y$[/tex] min: -10, [tex]$Y$[/tex] max: 10

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