Math Forum Discussions

MaryAnn Casey

Posts: 13
Registered: 12/3/04

Re: graphing quadratic equations
Posted: Apr 16, 2010 4:08 PM

Plain Text

I make them find the vertex first and then put that x value in the middle of the table of values on their paper. They can find the x value of the vertex using the calc. or x= -b/2a. They need to scroll the table until they get the numbers on either side of it - at least 3 of each. I tell them the graph to make the graph symmetric when they are finished so they don't give me a lopsided graph. They may have to scroll up and down on the table to get more values the graph in order to make it "even".

MaryAnn Casey
Math Lead Teacher
Saugerties HS

>>> "Virginia KURYLA" <VKuryla2@williamsoncentral.org> 4/16/2010 3:02 PM >>>
Thanks for all the feedback.

Here's my follow-up question.

Is there a way that we can give students the values that we want them to use for the table but still have them graphing with arrows? Do you have an example of how a question could be worded?

Would this be OK?
Graph the function x^2 + 4x + 7 for all real numbers. Use the interval ________ to create your table.

Thanks again!!
Ginny Kuryla

>>> "Betty Worthington" <worthington@pavilion.k12.ny.us> 4/16/2010 11:55 AM >>>
You are correct, when given an interval you don't use arrows.

>>> "Virginia KURYLA" <VKuryla2@williamsoncentral.org> 04/15/10 3:23 PM >>>
Hello,

I am currently pushing into an 8th grade Math class to provide AIS services. We are working with non-linear equations and are showing students how to graph quadratics without the benefit of a graphing calculator. We decided not to teach them to find the TP and Axis of Symmetry yet so we wanted to give them the points. We used the format of graphing on the interval -2 < x < 2 to give them exposure to reading and interpreting interval notation. During the lesson the classroom teacher looked at me and asked if we should put arrows on the graph and continue beyond -2 and 2. We decided not to put arrows because we both remember a conversation with our HS colleagues in which it was decided that graphing on the interval means that there is a beginning and an end.

We are pretty sure that the conversation was related to a Regents question and that State Ed was called and they said that arrows made it in-correct when graphing on an interval. We grabbed the red course 1 books for verification, but they give the interval for the table and include arrows on the graphs. I tried to go through the old exams to figure out which one we were grading that this was an issue, but couldn't find anything like that.

Does anyone have any thoughts about arrows vs. no arrows with this language.

Thanks for your help!!

Ginny Kuryla

Virginia Kuryla

Williamson Central Schools
AIS Math Teacher - Grades 3, 4, 5 & 8
Math Curriculum Coordinator gr 5-8

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