HiddenJewel Posted October 24, 2009 Share Posted October 24, 2009 I really need some help on Unit 6, Part B, Lesson 4 Rational Expressions. The solution manual shows problems 8 and 10 being solved by finding the least common multiple of only one side of the equation. The video and the course notes show finding the LCM for both sides. Why are they only using the LCM for the one side? I think I understand why you can do just the one side because you are just multiplying the fractions by 1 so not changing their value. But it just bugs me when a problem has to be solved a different way than the instructions show. And how are we supposed to know when only to find the LCM for one side and when to find it for both sides? This was never discussed in the lesson. Thanks. Quote Link to comment Share on other sites More sharing options...
Musicmom Posted October 24, 2009 Share Posted October 24, 2009 You might want to check with Videotext on this one. Since Module E is newly out, it could be an error in the book. We haven't done Module E--finished D two years ago, and had to switch to something else because E wasn't out yet (Can't believe it took 2 years! :eek: They called me last week to let me know they were ready to ship it to me :001_huh: Uh... ds has now finished calculus... still it was very nice of them to keep my order all this time, and it is a good company. But I digress...) Anyway, we had to use pre-production materials when we started D and then finished with the 1st edition of the books--there were many errors, and some really confusing answers in the key which I should have taken the time to call about and get straightened out. Quote Link to comment Share on other sites More sharing options...
HiddenJewel Posted October 24, 2009 Author Share Posted October 24, 2009 You might want to check with Videotext on this one. Since Module E is newly out, it could be an error in the book. We haven't done Module E--finished D two years ago, and had to switch to something else because E wasn't out yet (Can't believe it took 2 years! :eek: They called me last week to let me know they were ready to ship it to me :001_huh: Uh... ds has now finished calculus... still it was very nice of them to keep my order all this time, and it is a good company. But I digress...) Anyway, we had to use pre-production materials when we started D and then finished with the 1st edition of the books--there were many errors, and some really confusing answers in the key which I should have taken the time to call about and get straightened out. Thanks. I bought my modules used and have not paid the $99 for tech support. So I can't really contact VT on it. I forgot to put in my title that I am talking about VT Algebra. I saw that the Geometry Module E just came out. My Algebra Module E is from 2000. Quote Link to comment Share on other sites More sharing options...
Musicmom Posted October 24, 2009 Share Posted October 24, 2009 Thanks. I bought my modules used and have not paid the $99 for tech support. So I can't really contact VT on it. I forgot to put in my title that I am talking about VT Algebra. I saw that the Geometry Module E just came out. My Algebra Module E is from 2000. Whoops... :blushing: guess I have Videotext Geometry on the brain since my dd is starting that this year. She did Module E of the Algebra last year, so I'll try to look this up and see if we have any insight. Quote Link to comment Share on other sites More sharing options...
HiddenJewel Posted October 24, 2009 Author Share Posted October 24, 2009 Whoops... :blushing: guess I have Videotext Geometry on the brain since my dd is starting that this year. She did Module E of the Algebra last year, so I'll try to look this up and see if we have any insight. Thanks. Quote Link to comment Share on other sites More sharing options...
Musicmom Posted October 25, 2009 Share Posted October 25, 2009 I looked it up and I see what you mean. We have the 2003 edition, and Lesson 4 is called Literal Equations, but hopefully the course notes and problems are the same. My best guess at explaining it is that you’re working with fractions, so the overall goal is to get rid of them. To add or subtract fractions, any fractions, you first have to get a common denominator (which is what the LCM is all about—it gives you the lowest common denominator you can use). Now, you could go to a common denominator for the whole equation at once, if that’s helpful, which is what the course notes show. But it’s perfectly legitimate also to work in stages and just go to a common denominator for the fractions that are being added (in other words, if you have 1/3 + 1/6 = 1/2, it’s fine to go to 6ths on the left side and leave the ½ as is—you haven’t changed the equation.) This is what’s happening in the solution to #8. They just obtain a common denominator (the LCM) for the fractions being added, and then it’s a simple matter to multiply the whole equation by b/1 (to get rid of the 1/b) and proceed to solve for b. In the course notes, where they’re working with the R’s, it was expedient to go to a common denominator for the whole equation and then solve for r1. I hope this makes sense… I agree it’s frustrating and confusing when they show you only one method in the course and then use another in the solutions. There’s usually more than one way to approach a problem and I wish they would demonstrate that flexibility a little more before they use it! Hope this helps at least some! Quote Link to comment Share on other sites More sharing options...
HiddenJewel Posted October 25, 2009 Author Share Posted October 25, 2009 That does help. Thank you much! Do you know when you should find the LCM for all fractions and when to find it for just one side? Quote Link to comment Share on other sites More sharing options...
HiddenJewel Posted October 25, 2009 Author Share Posted October 25, 2009 The other thing is that I tried to solve both #8 and #10 by changing all the denominators to the LCM and I could not get them to work out. Quote Link to comment Share on other sites More sharing options...
Musicmom Posted October 26, 2009 Share Posted October 26, 2009 I tried out #8 also... I'm sending you a pm with the details. Quote Link to comment Share on other sites More sharing options...
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