Lines can be used to approximate a wide variety of functions; often a function can be described using many lines. If a stock price goes from $10 to $12 from Ja

Question

Lines can be used to approximate a wide variety of functions; often a function can be described using many lines.

If a stock price goes from $10 to $12 from January 1st to January 31, and from $12 to $9 from February 1st to February 28th, is the price change from $10 to $9 a straight line?

How can I use two “pieces” of lines to describe the price movements from the beginning of January to the end of February?

Answer 1

To add to Mark's solution, since the price increases at a certain time interval and then decreases at another time interval, we can say the situation is possibly represented as a negative parabolic function.  It is also possible that it can represented by a negative absolute function as well.

Answer 2

On of the very best examples of a plot with many, many line segments is the Stock Market prices.

 

This line has two segments and is not a straight line.

 

In math, we write multiple equations and then specify when they should be used.  For example:

     For phone calls:

          10 cents/min   (midnight to 8 a.m.)

          15 cents/min   (8 a.m. to midnight)

 

For this problem:

  Stock price is:

          $10 + ((12-10)/31)*day      (for January days)

          $12  - ((-9-12)/28)*day       (for February days)

Answer 3

From January 1 to 31 the line has a positive slope - goes up from left to right.

From February 1 to 28 the line has a negative slope - goes down from left to right.

 

It is not a straight line.