Tuesday, May 04, 2010

Graphing Parabolas

I had really good luck with this sheet when we were practicing graphing parabolas today. I apparently haven't been doing enough graphing in class because I still got a handful of questions during class, "how do I find points on the graph". Scary. Anyway, I'm not too worried because with other topics earlier in the year that they couldn't do, now they're great at them (like terms, solving for x, ...). We only got through this front side because of all the other extra administrative stuff we needed to take care of.

What I like about having a preprinted sheet is that I can stop them at each step and have a discussion: why is it called the axis of symmetry? how do you know what x value to plug in for the vertex? what kind of shape is the axis of symmetry (a point or a line or other?), how do you know how to find the y-intercept? why? does every parabola have a y-intercept? (that brought surprising answers when I asked for thumbs up for yes and down for no) ....


  1. I tried something difference this year with my Algebra B students. Instead of teaching them the formula for axis of symmetry, I showed them how to put the equation into vertex form like in Algebra 2. I was really impressed at how well they picked it up. Of course, when the lead coefficient isn't 1, then I showed them the formula. Most still preferred the vertex form though.

  2. In a graphical wave form, a parabola which opens up has a lowest point and a parabola which opens down has a highest point and the highest or lowest point on a parabola is called the vertex.