Showing posts with label Rational Functions. Show all posts
Showing posts with label Rational Functions. Show all posts

Thursday, 30 November 2017

Rational Functions Continuum

We are continuing to develop a series of "Continuum" activities. In these activities, students are given basic knowledge questions on cards from an envelope. On each card there is one type of question. When the student completes a set number of questions on their card correctly, they then replace that card and grab a new card from the next envelope. This next envelop will typically have problems of a similar (to each other) type but incrementally more difficult than the previous envelope. In this way students move from simpler to more difficult questions at their own pace.

Here we have two sets of cards. On one set we have rational equations that start with simple ratio type questions and move to rational equations with polynomials. The second set are similar in style but are created from rational inequalities. In each case, as students move through the cards, the questions become more difficult.

Note that if you look at the expectations, they both say "simple" equations/inequalities but as you move to the last few cards, you may not consider those simple. That is purposeful. We create the cards so that the first one is easy enough for everyone but the last one(s) may go beyond the curriculum so that kids who are not struggling have some place to go that may be challenging. As a teacher, you should decide which card is the level that you hope all students will reach. For other rational function activities to investigate their nature, check out our other post here.

Typically when we have done these, students could check their answers by using a UV pen to reveal the answers written on the answer cards (see example from our fraction continuum to the right). This adds a bit of "magic" to this activity that the students tend to enjoy making them work just a little harder.
  • MHF4U 3.6 - solve simple rational equations in one variable algebraically, and verify solutions using technology
  • MHF4U 4.2 - determine solutions to polynomial inequalities in one variable [e.g., solve f(x) ≥ 0, where f(x) = x3 – x2 + 3x – 9] and to simple rational inequalities in one variable by graphing the corresponding functions, using graphing technology, and identifying intervals for which x satisfies the inequalities
  • Enough copies of each of the question cards for your class (there are six cards per page at each level except the last) in different colour card stock for each level, laminated (use colours that allow seeing the magic pen writing - you may want to test this). You will likely not need as many cards in the last few envelopes as students work at different paces. 
  • The answer cards are the same as the question cards but you write the answers in invisible ink on them. To help distinguish the answer cards to the question cards you should put a stamp or sticker on the back. Write on the cards first then laminate them. If you write on the card after lamination then the ink tends to wear off. There are sample answers at the end of each document. That is for you to carry around (or not) but not for showing students - more for your reference.
  • The "magic" pens can be purchased at Chapters/Indigo or we found these at a Scholastic's book fair. We have since purchased some on eBay or Amazon.

  1. Place the questions in piles (or in envelopes taped to the wall) in order of difficulty and set up three stations for the answer cards. Students will get a card and answer the first 4 questions (you might choose less or more questions to answer but typically choose a number so that if they don't get them all correct, there are enough questions left on the card for them to practice more). 
  2. You could have all students start at level 1 but for this activity to be most successful, students should start at the appropriate envelope. If they start in one that is too hard they will be frustrated and if they start in one that is too easy they will be bored. Use an exit card (the day before) to help you decide which envelope each student should start in. When giving back the exit card write down the colour card they will start in. 
  3. Students may decide to do one question at a time and then go check their answer or they may do all 4 and then check. Students are monitoring themselves so they decide. If they get the first 4 right, they have a level of mastery to move themselves to the next card. If not there are more questions on the card until they master that type. You can decide whether you want them to do the other 2 or just do enough to get a total of four correct. 
  4. As they move through the continuum, the hope is that they reach the level that you decide equates to "simple" but not too hard4. You may wish to have them do all the questions on that card. 
Note that we have been having some issues with Google Docs reformatting the cards depending on what machine or browser you are using. This seems especially true with these cards where there are so many equations. So you may have to reformat when you make your own copy. For a good version, just use the PDFs.
Did you use this activity? Do you have a way to make it better? If so tell us in the comment section. Thanks

Friday, 24 February 2017

Investigating Graphs of Rational Functions

In Ontario in our grade
12 advanced functions course we are to graph rational functions that are reciprocals of linear and quadratic functions and ones where both the numerator and denominator are linear functions. In this post there are several activities (both hands on and electronic) that could be used throughout a unit on graphing Rational Funcitons. Here, we start with an investigation that is done with students in groups graphing reciprocal linear and quadratic functions by hand and then ends with a Desmos Card sort. There is also a Desmos investigation on functions in the form   and a consolidation activity using Desmos Marbleslides. Lastly, there is an assignment challenging students to create their own Which One Doesn't Belong. Note that you may not want to do all of these activities while doing this unit. Just pick and choose.

  • MHF4U 2.1 - determine, through investigation with and without technology, key features (i.e., vertical and horizontal asymptotes, domain and range, intercepts, positive/negative intervals, increasing/decreasing intervals) of the graphs of rational functions that are the reciprocals of linear and quadratic functions, and make connections between the algebraic and graphical representations of these rational functions.
  • MHF4U 2.2 - determine, through investigation with and without technology, key features (i.e., vertical and horizontal asymptotes, domain and range, intercepts, positive/negative intervals, increasing/decreasing intervals) of the graphs of rational functions that have linear expressions in the numerator and denominator, and make connections between the algebraic and graphical representations of these rational functions
  • MHF4U 2.3 - sketch the graph of a simple rational function using its key features, given the algebraic representation of the function
  • Chart paper or vertical surfaces for the investigation (markers etc)
  • If you choose to do the hands on card sort then you need to make copies of this set of cards (one per group). We usually make these on card stock and laminate them for durability.
  • If you choose to do the Desmos card sort then you need to have technology for your students. 

Activity 1: Reciprocal linear and quadratic functions

  1. Put students in groups of no more than three. They can work on vertical surfaces or at a table.
  2. Each group is given one set of a linear equation and its corresponding reciprocal (or rational) function. There is enough sets for 11 groups. They are to graph each on the same axis. Afterwards they should determine any intercepts and/or equations of asymptotes (see answers to the right).
  3. Once complete they should walk around the class to see other sets and come to some conclusions as to properties of linear functions and their corresponding rational functions.
  4. Once complete there is a couple of follow up questions to check their thinking. 
  5. Next each group gets a set of quadratic functions and corresponding rational function. They are to graph each on the same axis. Afterwards they should determine any intercepts and/or equations of asymptotes. 
  6. Again, once complete, they should walk around the class to see other sets and come to some conclusions. 
  7. There is another set of follow up questions to check their thinking (note, if time is a problem students can do a similar investigation for homework with this Desmos activity instead of the above steps). 
  8. As a follow up (maybe next day) you can do this physical card sort or this Desmos card sort. The Desmos card sort has some follow up questions to consolidate some of the ideas. 

Activity 2 Graphs in the form  


  1. Students complete the Desmos Investigation. This can be done in class or as a homework assignment.
  2. As consolidation, students can check what they know with this quiz. This can be done using paper and pencil (copy double sided then cut in half) or via this online Google Form. Note that if you use the form, click on this link and then choose advanced options (3 vertical dots) to make a copy. Please do not edit our form.

Activity 3: Desmos MarbleSlides for  

  1. To show if they understand the investigation from Activity 2, students can complete this Desmos MarbleSlides. The first few slides are just to show some possible solutions and then the challenges start. Note that students may have to work with the domain of the function to become successful. 

If you want to know how to create your own Marbleslides, watch this video

Activity 4: Which One Doesn't Belong Assignment

  1. As a review you might choose to assign students to create their own Which One Doesn't Belong (http://wodb.ca/). The goal here is to create four graphs such that each of the graphs could be chosen as the one that doesn't belong based on specific criteria.

Did you use this activity? Do you have a way to make it better? If so tell us in the comment section. Thanks