Two young mathematicians discuss how to sketch the graphs of functions.
- Devyn
- Riley, OK I know how to plot something if I’m given a description.
- Riley
- Yes, it’s kinda fun right?
- Devyn
- I know! But now I’m not sure how to get the information I need.
- Riley
- You know, I’d like to make up a procedure based on all these facts, that would tell me what the graph of any function would look like.
- Devyn
- Me too! Let’s get to work!
Below is a list of features of a graph of a function.
- (a)
- Find the points where goes to infinity as goes to (from the right, left, or both). These are the points where has a vertical asymptote.
- (b)
- Find the critical points (the points where or is undefined).
- (c)
- Identify inflection points and concavity.
- (d)
- Determine an interval that shows all relevant behavior.
- (e)
- Find the -intercept, this is the point . Place this point on your graph.
- (f)
- Find the candidates for inflection points, the points where or is undefined.
- (g)
- If possible, find the -intercepts, the points where . Place these points on your graph.
- (h)
- Compute and .
- (i)
- Analyze end behavior: as , what happens to the graph of ? Does it have horizontal asymptotes, increase or decrease without bound, or have some other kind of behavior?
Here is one possible answer to this question. Compare it with
yours!
- (a)
- Find the -intercept, this is the point . Place this point on your graph.
- (b)
- Find any vertical asymptotes, these are points where goes to infinity as goes to (from the right, left, or both).
- (c)
- If possible, find the -intercepts, the points where . Place these points on your graph.
- (d)
- Analyze end behavior: as , what happens to the graph of ? Does it have horizontal asymptotes, increase or decrease without bound, or have some other kind of behavior?
- (e)
- Compute and .
- (f)
- Find the critical points (the points where or is undefined).
- (g)
- Use either the first or second derivative test to identify local extrema and/or find the intervals where your function is increasing/decreasing.
- (h)
- Find the candidates for inflection points, the points where or is undefined.
- (i)
- Identify inflection points and concavity.
- (j)
- Determine an interval that shows all relevant behavior