For Math Teachers Bob's math musings and ideas about teaching math This part of bobprior.com is in its infancy, and has few articles at this time. Please check back occasionally. If you haven't seen any new articles, write to me and bug me about updating it. You can reach me at bob.prior@rcc.edu . Please put "bobprior.com" in the subject line. Some of these are in a pdf format and Adobe Reader is required to open them. If you do not yet have Adobe Reader on your hard drive, then you may get a free download from Adobe. (It is a safe download. Be sure to follow the instructions on the page.) 1. Developing the Quadratic Formula Here, I show a variety of ways to develop the formula, including a graphical method I developed. The explanation of the graphical method first develops the graphing of a parabola and its various features. I challenged myself to "discover" the graphical approach after pondering the question, "Is it possible to develop the formula without ever having to complete the square?" I believe that my graphical approach does exactly that. Also, two "ancient" methods are shown, the Babylonian method and a geometric method. The Babylonian method actually develops a Quadratic Formula, whereas the geometric method just solves a quadratic equation. A. The Traditional Approach B. The Babylonian Approach C. The Geometric Approach D. The Graphical Approach 2. The Order of Operations I contend that the order of operations used in arithmetic, algebra, etc. is not an arbitrary order to which mathematicians the world over decided to agree. I contend that the order of operations must be the way it is. Here is my position paper on The Order of Operations: Math or Myth 3. Mathematical Tidbits Here are some mathematical tidbit that may interest you. I presented these as handouts at the AMATYC Conference in San Diego, November 13, 2005. A. Math Tidbits Some of these are related to the Order of Operations handout. B. Dividing Fraction Why we invert and multiply. C. Divisibility Rules A list of the divisibility rules for 1 through 11. D. Divisibility Rule for 7 A thorough look a the divisibility rule for 7. In this paper, I prove that the rule works 100% of the time. I also show the divisibility rule for 13 and show how you can develop divisibility rules for 17 and 37, and a new rule for 11! 4. Math to Go: Podcasting Lessons A. Podcasting Presentation Handout.doc at AMATYC November, 2007 B. Practice Streaming Video-1 (brief clip, 1:00 in length) C. Practice Streaming Video-2 (brief clip, 1:26 in length) D. Factoring Trinomials Video (full clip, 28:24 in length) 
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