Line Week -- Day 2 - Graphing slope and y-intercept in Excel

So today was day 2 of Line week and it went okay, but not as well as the first day.  We spent our class period creating a spreadsheet in microsoft excel that had 2 lines where we could easily adjust the slope and y-intercept of each line.  I was hoping we could do that in 20-25 minutes, it took about 30 minutes, which left only 15 minutes for plugging in different values (here is the file).

We started with shifting one curve over the other (using y-intercept), making one curve steeper (using slope), one student quickly discovered parallel lines, and so on.  We were able to play around and some students started noticing how the y-intercept effect the "vertical position" of the line (yippie!).  When I asked how they could guarantee the lines crossed in our viewing screen they figured out the idea of using positive slope in one equation and negative slope in the other.   (Tomorrow we see if they figure out using the same y-intercept!)

The graph started to lead to good discussion and reinforced the slope lesson, but we were not able to finish with why mx and b are like terms, which I hoped to do per my previous post.  We will need to pick up tomorrow with placing units on our equations to help give it a context!

So it did not go as well as hoped, but we still created an excel spreadsheet that can now be used to solve 2 equations for 2 unknowns where the ordered pair are integers between -6 and 6!  And we will continue tomorrow with line week - using our spreadsheet to find more relationships and make/test hypothesis.  Then we will move to looking at plotted lines and figuring out formulas -- I am thinking a Jeopardy format - I plot the line on screen, they answer the equation in the form of a question - "What is y = 3x - 2?"

Overall another good day!

Line Week! Slope, slope, slope....

Slope & lines, lines & slope.  It is  truly one of the most important concepts in Algebra - if truly understood many things are easy, if simply memorized it leads to many forgetful problems.  So with that thought in mind I am setting up "Line Week" -- like "Shark Week" - except cooler and many more attacks resulting in gruesome death (students love the joke...).

So I made the joke(s) last week, and now I sit here Sunday morning trying to create the lesson that really results in students understanding of slope, intercepts, etc.  I teach 8-12th grade - so these students have seen (and forgotten) lines, they have been using x,y tables to plot points and create lines -- but with no real world understanding of slope etc.  {You may think what kind of person promises "line week" without a plan...  - well I do!  Lines are important and it is time for lines!}

I have spent the last 2 hours combing the internet for something (and if you pictured Mel Brooke's Space Balls combing the desert you're my kind of person) and have really not found anything amazing.  I have founded some fun songs - that I may use once they understand.  And some good worksheets, I may use those once they can do at home alone (in a month) for practice.  But nothing that really ties Rise over Run to y =mx + b....

My plan is to use a stair step example that I read about on I Want to Teach Forever, but then I want to tie slope and the slope-intercept equation.  It is units that will do it!  Perhaps it will be dollars per day for slope, thus using x as days - mx will become dollars...  b is dollars initial and thus with some practice the two will make sense.  That is the tie, seeing that mx and b are the same units (thus like terms).  Then zero slope is no money, and undefined slope is winning the lottery.... or being robbed.....

Hopefully there will be another post of something amazing, or at least acceptable...  Cause from combing the internet there seems to be very little that teaches the concept - just simply the procedure.