Mathematical+Reflections,+p+82+0910

S. Z. 11 Apr 2010 Big Idea: Negative numbers help us to model many real word situations. E. Q. #5: How do I use coordinate grids? NOTE: I will use + for positive and – for negative. Answer: If the X value is + and the Y value is +, it is in quadrant I. If X is + but Y is -, it is in II. If X is – and Y is -, it is in III. Finally, if X is – and Y is +, it is in IV.
 * __Mathematical Reflections #5__**
 * 1. How can you tell which quadrant point will fall in by looking at its coordinates?**

Answer: For problems such as Jean’s, it would probably make most sense to look at quadrants II and I. This is because she wants to figure out how much profit she will make from her business. Because her initial funds are -$800 and she hasn’t made any tune-ups yet, Y would equal -800 and X would equal 0. It isn’t possible to make less than 0 tune-ups, so quadrants III and IV (which contain negative X values) would not be needed. At first glance, it would seem that quadrant I isn’t needed, but as Jean makes more tune-ups, her profits would eventually reach above 0. Quadrants I and II would therefore make the most sense in real life situations.
 * 2. You have looked at several problem situations in which you figured out how to make a table of data. You also learned that if you can write an equation to describe how the variables are related, you can use a graphing calculator to graph the equation. How do you figure out what part of the entire graph actually makes sense in the real problem situation? Use an example to help explain.**

In this investigation, we learned how to use coordinate grids and how to plot formulas on graphing calculators. Coordinate grids have two axes, X and Y, with different values that show different points on the grid. In order to name these points, the format of (X,Y) is used. To plot formulas that make graphs on a graphing calculator, we first assign a variable as the Y value (which must be isolated), and then one as an X value. Then, we plot them in the calculator. Sometimes, these results are not visible, so we use the WINDOW and ZOOM functions to view the whole grid. Finally, we figured out how to get the useful data from the grid by using these two functions to view a specific part of the graph.
 * __Summary__**