Graphing a function using calculus

In summary, to graph the function (x^2-9)/(x^2-4), you first divide out the polynomial to get something like f(x) + (something)/(x^2-4). Then, find the critical numbers by finding the derivative of the function and setting it equal to zero. The critical numbers for this function are where the derivative is equal to zero. Next, factor (x^2-4) and see what happens as x approaches ±2. Finally, to determine concavity, find the second derivative of the function and analyze the sign of the numerator and denominator. This will tell you the intervals where the graph is concave up or down.
  • #1
Sniperman724
66
0
How would you graph the function:
(x2-9)/(x2-4)

I am having a lot of trouble finding the critical and hypercritical numbers without the aid of a graphing utility.
Thank you very much!
 
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  • #2
Sniperman724 said:
How would you graph the function:
(x2-9)/(x2-4)

I am having a lot of trouble finding the critical and hypercritical numbers without the aid of a graphing utility.
Thank you very much!

Start by dividing out the polynomial to give you something like:

y=f(x) + (something)/(x2-4)

Then factor (x2-4) and see what happens as x→±2.
 
  • #3
To get the critical numbers, find the derivative of (x^2 - 9)/(x^2 - 4). The critical numbers are those for which the derivative is zero.
 
  • #4
yea, i understand that, but I calculated the second derivative to be (-30x2-40)/(x2-4)3, which has two asymptotes at 2,-2, but the top of this fraction can never equal zero and I end up with imaginary numbers. How do you solve for concavity with imaginary numbers?
 
  • #5
Where is the first derivative equal to zero? You seem to have skipped right over that step.

I got the same as you for the second derivative, so that would suggest that we're both right. The numerator is always negative for any real number, but the denominator can be positive or negative, depending on whether |x| > 2 or |x| < 2, respectively. That tells you the intervals where the graph of the function is concave up or down.
 

1. What is the purpose of graphing a function using calculus?

The purpose of graphing a function using calculus is to visually represent the behavior of the function and gain a deeper understanding of its properties. It allows us to see how the function changes over its entire domain and helps us to analyze its critical points, intervals of increasing or decreasing, and concavity.

2. How do you determine the critical points of a function on a graph?

To determine the critical points of a function on a graph, you can take the derivative of the function and set it equal to zero. The x-values where the derivative is equal to zero are the critical points. These points can also be found by looking for any sharp turns or points where the slope changes from positive to negative or vice versa on the graph.

3. What is the significance of the concavity of a function on its graph?

The concavity of a function on its graph represents the rate at which the function is changing. A function can have either a concave up or concave down graph. A concave up graph means that the function is increasing at an increasing rate, while a concave down graph means that the function is increasing at a decreasing rate. The inflection points, where the concavity changes, can also provide important information about the behavior of the function.

4. Can calculus be used to find the maximum and minimum values of a function on a graph?

Yes, calculus can be used to find the maximum and minimum values of a function on a graph. By taking the derivative of the function and setting it equal to zero, we can find the critical points. Then, by using the second derivative test, we can determine whether these critical points are maximum or minimum points on the graph.

5. How does calculus help in understanding the overall shape of a function on a graph?

Calculus helps in understanding the overall shape of a function on a graph by providing information about the behavior of the function at different points. This includes information about the slope, concavity, and critical points of the function. By analyzing these aspects, we can gain a better understanding of the curve of the function and how it changes over its domain.

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