5.2.1Introduction to Limits
Limits• Today you will follow the travels of Benny and Bertha Bug.
With their help, we will look at graphs of rational functions and piecewise functions from a bug’s eye view to help convey the important concept of limits in an intuitive way.
5-41. Sketch the graph of f(x) = + 3.
Place a bold dot on the point of the graph corresponding to x = 5.
Benny Bug starts at this location and crawls along the curve, moving to the right.
If he keeps going in this direction, what y-value does Benny think he’s getting closer to? _____
As Benny keeps going farther and farther to the right, how low does Benny think he will get? _____
5-42. Consider the graph below when answering the questions below.
5-43
Look at your graph of f(x) = + 3
As x gets larger and larger, f(x) gets closer and closer to 3.
MATH NOTES - Definition of a One-Sided Limit
• The formal definition of a limit is well beyond this course. If you take engineering or calculus, you will get it there. For now you need to understand the basic notation.
• We say x → c+ if the values of x get closer and closer to c from the right; that is, x > c. Similarly, x → c− if the values of x get closer and closer to c from the left.
MATH NOTES - Definition of a One-Sided Limit
• If f(x) gets closer and closer to a given number L as x → c+, we say, “The limit of f(x) as x goes to c from the right is L.” This is written as .
• If f(x) grows without bound we say .
• If f(x) gets closer and closer to a number M as x → c−, we write .
MATH NOTES - Definition of a One-Sided Limit
You should know that although most college textbooks give ∞ as a limit (as shorthand for f(x) growing without bound), some books say “no limit.”