Showing posts with label exponential functions. Show all posts
Showing posts with label exponential functions. Show all posts

Thursday, May 29, 2008

Schlope and PMAN

Mathematics is the art of giving the same name to different things. - Henri Poincare
So in this case it is not the quite the same name, but I have sort of "invented" some terminology. The idea of "schlope". Schlope is quite similar to slope. The slope of a line tells you how much to go up for every 1 that you move to the right. Schlope tells you what to multiply by for every one step to the right. Schlope is very important for exponential functions. Generally, in exponential situations we talk about the "rate of growth". If the rate of growth is 8% then the function that models that growth has "1.08 to the t" in it. That 1.08 is what I call "schlope". So, schlope is the number that you actually use in the formula.

In fact, you can create parallels for all your favorite formulas and constructs from linear functions. This parallel construction highlights another construct of mine that I like to call the hierarchy. The hierarchy is simply the recognition that the fundamental ways of putting numbers together come in an order. At the bottom level we have Addition and Subtraction. In the middle we have Multiplication and Division, and at the top powers, roots, and logarithms. Another teacher at my school refers to this as "PMAN" for powers, multiply, add, nothing. It is very helpful to think about PMAN when doing calculations with exponents and logs. If you are taking powers of powers, "P", then you "M"ultiply the powers. If you are "M"ultiplying powers with the same base then your "A"dd the exponents. If you are "A"dding different powers of the same base together then you do "N"othing.

To move from Linear functions to Exponential functions you simply must move up in the hierarchy. Moving from repeatedly adding a number to the height every time to multiplying that height by some fixed number. The formulas can be written quite similarly:



Wednesday, May 28, 2008

Are quadratics really that important

If I was a student who had just finished a course in Algebra I in most schools across America I think that I would think that the following were the most important things that we had done. I would think this because we had spent so much of our efforts on it.

  • linear equations
  • distributive law
  • quadratic equations
  • factoring
The problem with this list isn't so much what is on it, it is what isn't on it. It seems to me that we simply must include exponential functions and therefore also logarithms. I guess my question is, "Are quadratics really that important?"

The only way to add these topics in is to take other topics away. So what can go? Here is a partial list of topics that might be cut or reduced in the standard curriculum.

  • completing the square
  • conics
  • rational root theorem
  • long division of polynomials
Exponentials seem like such a natural topic, and one that could be made to support and build on linear equations so beautifully. I will give more of this idea when I write later about "schlope".