A continuous function is one that we can draw without lifting our pencil, pen, or Crayola crayon.
Here are some examples of continuous functions:
If a function is continuous at x = c we can start with our pencil a little to the left of x = c and trace the graph until our pencil is a little to the right of x = c, without lifting our pencil along the way.
We will now return to those functions that are continuous at x = c. We can trace each function with a pencil, from one side of x = c to the other, without lifting the pencil.
If a function isn't continuous at x = c, we say it's discontinuous at x = c.
This function is not continuous at x = c, since the function isn't even defined at x = c. We can't compare the value f(c) to doesn't even exist!
This function "jumps" at x = c. To draw the graph we would have to draw one line, stop at x = c and lift the pencil, then draw another line. As far as the limit definition goes, doesn't even exist (the onesided limits disagree). Therefore we can't possibly have
This function also jumps at x = c. To draw the graph we would have to draw a line, lift the pencil and draw a dot at x = c, then lift the pencil again to draw the remaining line. In this graph
both f(c) and
exist, but the function value disagrees with the limit.
If a function f is discontinuous at x = c, then at least one of three things need to go wrong. Either
In other words: for a function f(x) to be continuous at x = c, three things need to happen:
Look at the graph of the function f(x). The following three statements must all hold for f to be continuous at c.
For each given value of c, determine whether each of the three statements holds. Use this to determine whether f is continuous at the given value of c.

Look at the graph of the function f(x). The following three statements must all hold for f to be continuous at c.
For each given value of c, determine whether each of the three statements hold. Use this to determine whether f is continuous at the given value of c.

Look at the graph of the function f(x). Determine whether the function f is continuous at each given value. If not, explain.

Look at the graph of the function g(x). Determine whether the function g is continuous at each given value. If not, explain.
