Tag Archives: equations

An Algebraic Epiphany

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People, this post is why I love the #MTBoS.  You can’t read everything, learn everything, critically think about everything; but if you read blogs and tweets, then you can collect more of that knowledge than you would alone. So even though I am not participating in the #intenttalk book study/chat (Am I the only one who always thinks it’s Kimmie Schmidt on the cover?), I did see this tweet from Bridget:

I used that method a wee bit this year when I taught inverse functions and a few students really latched onto it. But now I’m thinking of starting this way on day one,  building on it, and tying it into Glenn’s three rules of mathematics. I sat down and played with it a bit for the last few days and all I can say is:

Are you ready for this?  Ok, let’s just dip our toes in:

Flowchart math from megcraig.orgThe main idea being that we think through the equation “forwards” and then work back to the solution using inverses. Another easy one:

Flowchart math from megcraig.orgI like (a) completing the circle of life by checking our answer and (b) each column showing equal values.

How about we try out the shallow end:

Flowchart math from megcraig.org Flowchart math from megcraig.orgYeah, I’m totally digging the two arrows for square root, too.

Flowchart math from megcraig.orgAre your ready to put your head underwater?  Ok, here it is….wait for it…

Flowchart math from megcraig.org

So one place where this method has problems is if there are variables on both sides. But I want to use this more as an introduction in each section, not a method for solving each individual equation. However, we can use the fact that each column is equal to set up the rest of the problem and finish with quadratic formula.

Now I thought for sure this could not work with quadratics. OR COULD IT?

flowchart math from megcraig.orgOk, so the weird thing here is that (a) my new erasable markers don’t like it when you rewrite over something you just erased and (b) we have 2 places that x is involved, so 2 starting points. But then I don’t know how they are going to add to equal 6. But (spoiler alert!) we do know what has to happen if we’re going to multiply to equal zero…

flowchart math from megcraig.orgHere the two back arrows from zero come from the fact we had two x inputs. Pretty powerful, eh?  Let’s try it on some other tricky problems, like rational exponents:

flowchart math from megcraig.orgOk, guys, we’re going to jump into the deep end now….ABSOLUTE VALUE!

flowchart math from megcraig.org

Update: I was so excited about “un-absolute valuing” that I forgot to “un-multiply”. -6 should turn into 3, which would then turn into -3 and 3; and finally -6 and 0 as the answers. Which I probably would have noticed if I followed my own recommendation to circle back through.

Holy cow I’m in LOVE LOVE LOVE with having to “unabsolute value” as a step, because of course to “unabsolute value” you go back to positive or negative.

But wait, what about….

flowchart math from megcraig.orgOk, ok, a little tricky, but not undo-able.

Now I did have trouble with this problem:

flowchart math from megcraig.orgI wasn’t sure if my beginning value should be x or 5. When I tried it with 5, I thought of it as “If I’m at 125, what root would I need to get to 5?  Oh, the third  root. That means the original operation in the top line needs to be the inverse of the third root, which is cubing, which means x = 3.”

But if I keep my beginning value as x, then it leads into a nice intro/need for logs:

flowchart math from megcraig.orgAnd then I went crazy with the log problems!  (Although not pictured is two logs equal to each other, e.g. log (x + 7) = log (2x – 4). I’ll leave it as an exercise for the reader; it really is quite pretty.)

flowchart math from megcraig.orgflowchart math from megcraig.org flowchart math from megcraig.org flowchart math from megcraig.orgThe last one being another case of, “Uh-oh, need to rewrite this as something isn’t so ambiguous.” Another case of that:

flowchart math from megcraig.orgOk, ok, I don’t know why I didn’t have two starting x’s and then divide them, but isn’t it just beautiful how it works out this way?  So I went some more down that path:

flowchart math from megcraig.orgThen I thought of other problems that cause students anguish, and immediately thought of the difference between 2sin(x) and sin(2x):

flowchart math from megcraig.org flowchart math from megcraig.orgAfter this, my brain was pretty much done for the day.  Or at least, I thought it was. Then I had a shower thought (where all problems are solved): hey, wonder if I could tie it to graphing transformations?

flowchart math from megcraig.orgGAH!!!!!  So you go through all the steps, then find your parent function, in this case absolute value. You have to use inverses to get to x (minus three, or in this case three to the left) and OH I SHOULD HAVE PUT = Y AT THE VERY END BECAUSE THEN YOU TRAVEL “FORWARD” (stretch 2, down 4) FROM THE PARENT FUNCTION TO GET TO Y.

Another one?  ANOTHER ONE!

flowchart math from megcraig.orgI don’t know why you would want it, but if you did want all of these examples in one pdf, here you go. Now there are some drawbacks as I’ve mentioned: things need to be simplified first, somethings get a little wonky, how will this work for trickier equations; but I think Kayne sums it up pretty nicely:

Would love any thoughts/opinions/comments/suggestions/epiphanies!

HERSHEY’S TORTE! (and Alg II Unit 1)

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Equations from Megcraig.org

Yes, I am going to make you scroll through all of my NoteTakerMakers to get to the most delicious cake recipe in the entire world.   And, boy, do I have a lot a lot to share for this unit: number sets, order of operations, equations, inequalities, and absolute value equations/inequalities.  (Want more? Visit my new Alg II files page!)

Let’s begin with this HORRIBLE HORRIBLE first day of Algebra II notes. Hey, did someone say lots o’ definitions and then stupid review problems?  I’m interested! The good news is I’ve scrapped it for better things (e.g. Desmos Function Carnival), but you never know when you need a good number sets graphic organizer.  I usually just casually mention the sets as needed, but I think maybe this year, I’ll give each student a number and have them group themselves however they want. Maybe they’ll do even/odd, positive/negative, fractions/whole numbers, but then we could divide into even more specific groups?  And then reverse it: start engulfing each other until we are all one big happy Real Numbers Family?   Anyway, here’s the NTM:

Equations from Megcraig.orgFile here.

(Ok, less talk, more files, then cake!) Order of Operations:

Equations from Megcraig.org

File here.

I even tried doing a Talking Points for Order of Operations!

Equations from Megcraig.orgFile here.

Then I don’t even want to talk about my actual solving equations notes. I’m going to totally change them up next time. But for now, how about some Find The Mistake?

Equations from Megcraig.org

I only used Comic Sans to make my fellow teacher happy. Plus it can be counted as one of the mistakes to find!

File here.

And did someone say word problems?

Equations from Megcraig.org

I do so enjoy the travel chart, however, next year I’ll have them figure out what to do for each case instead of telling them.

File here.

And here’s the homework for these two sections:

Equations from Megcraig.orgFile here.

Now it’s time for some inequalities!  Algebra II is the first time the students see interval notation, so this year we played a match game:

Equations from Megcraig.org Equations from Megcraig.orgWord file here.  PDF File here-print 2 per page to get it all on the front of one sheet.

Full disclosure: it was a bit of a struggle and not sure if it was worth the time. I may revert back to this instead, or do a mixture next year.

Equations from Megcraig.org

File here.

I made a powerpoint for #1-14 so we could quickly go through them the next day in class, but you may want to use it for whiteboarding or review (each problem is animated step-by-step)

Equations from Megcraig.orgFile here.

These are the notes we did this year, jumping right into compound inequalities the same day:

Equations from Megcraig.orgFile here.

Next up, absolute value. I almost feel bad sharing this because I cannot teach this well.

Equations from Megcraig.orgFile here. Here’s how I fill in the top boxes:

Equations from Megcraig.orgMoving right along…

Some homework:

Equations from Megcraig.orgFile here

And some practice powerpoint for the whole chapter, heavy on absolute value:

Equations from Megcraig.orgFile here.

And the study guide, which as promised in my #MTBoSDirtySecrets, is very similar to my test.

Equations from Megcraig.orgFile here.

And now the moment you’ve all been waiting for!!!

My Thing

My thing today is Hershey Torte. This is the yummiest cake in the entire world. On Mother’s Day I tried to make a chocolate cake with peanut butter icing. The cake part went horribly, so I rescued it by making the cake portion of this with the peanut butter icing. Then, upon tasting the final result, questioned why I didn’t just make this to start with.  Warning: I cannot be left alone with this cake.

Hershey’s Torte

CAKE:

1 box German Chocolate cake mix
1 small package instant vanilla pudding
4 eggs
1 1/2 cup milk
1 cup vegetable oil

Mix well. Pour into 3 round (greased) pans and bake for 30 minutes at 325 degrees. Cool completely before frosting.

FROSTING:

Cream together:
8 oz cream cheese
1 cup confectioner’s sugar
1/2 cup granulated sugar

Add:
8 oz Cool Whip
1/2 cup pecans (optional if your husband is anti-nut)
6 Hershey’s plain chocolate bars, chopped fine

After you have mixed everything together, frost between layers and on top. Refrigerate.

One taste and then you’ll want to: