Guess My Rule

Date Nov. 5, 2005
Class Algebra 2
Teacher Becky Bruening
Notes Guess My Rule activity from the Analyze This.   It went over really well! 
Before each round I covered my view screen and entered an equation into my TI-83.  Then using the ASK feature on the calculator I had students chose a value for x, entered it in the calculator, and it showed the value for y.  Students then examined these values and tried to determine the rule for function (such as f(x) = _______ ) for each round.
The activity reinforced the idea of independent/dependent variables that we had just talked about, as well as some deep mathematical reasoning.
I only did it for about 10-15 minutes, giving a miniature tootsie roll to the first few students to write down the rule and show me, then awarded a “half-off any homework assignment” certificate to the person with the most tootsie rolls (or wrappers) at the end of class, so they were VERY motivated, and it kept the wrappers off the floor.
For the most part, they seemed to come up with the equations very easily – I even had to go away from strictly linear functions as I suspected that some students were quickly using the first two points given and finding the equation of the line.  (How wonderful to actually worry about them applying algebra!)  Even when I added the x^2 they found the rule quickly!
I was concerned about a few students who did not seem to come up with a strategy.  I would have liked to have worked together to have helped them find one – but of course the students who were winning were not interested in sharing their strategies!  For this reason I think it was probably best to keep it short. In the future I may try to use it in Algebra One instead – as it seemed almost too easy for the Algebra Two students.  I liked the 10-15 minute time frame – it seemed to hold the students' attention.  I think any longer and they (especially the ones who were not as good at the game) would begin to get bored.