Part+Seven

The Microsoft Office 2010 version of excel still handles negation and exponentiation as it did with Microsoft Office 2003. For example, the simple formula = -5^2 (the example provided in the article) is still calculated as 25. Likewise, the formula =0-5^2 still yields -25. Lee (2005) refers to this nuance as a “technological dark surprise” (p.560). In other words, this is a problem because Lee was expecting the spreadsheet package to calculate the formula = -5^2 as -25. However, I have always expected the software to calculate the same formula exactly as it did, due to my experience with Hewlett-Packard graphing calculators (HP 48G). On the other hand, I experienced the “technological dark surprise” of negation and exponentiation the first time I used a Texas Instruments graphing calculator (TI-83); and I am not the only one. My students continually assume that the square of a negative number results in a negative number simply because the TI-83 calculates it as such (see Lee’s expectation of Excel’s calculation above). This is of much greater concern for me because students are allowed to use the TI-83 on their state exam not Microsoft Excel. Furthermore, students will not be expected to evaluate a simple expression such as -5^2, for example. They will however be expected to evaluate the distance formula1 which may require them to find the square of a negative number, which is always positive. In the past, I would deal with this issue after-the-fact. Then I began to see the same error repeated year after year with students. Now I address the problem in advance warning students to place any numbers that will be exponentiated in parentheses. **References** Stohl, J.T. 2005. “Fool me twice, shame on me”. //Mathematics Teacher//, //98//(8), 560-563. **Endnotes** 1 
 * Part seven: Reflection of “Fool me twice, shame on me” article**