|
Welcome Guest | Login | |
|
Index
| Recent Threads
| Who's Online
| Register
| Search
| Help
| 
|
 |
WebGraphing.com Forum » List all forums » Forum: Precalculus and Trigonometry Homework Help » Thread: Is it my textbook, or is it me? |
|
Total posts in this thread: 2 |
[Add To My Favorites] [Watch this Thread] [Post new Thread] |
| Author |
|
flansbmp
|
I picked up the Pre-Calculus Workbook for Dummies to give myself a refresher before heading back to college after a 10 year hiatus. I've been working my way through the problems, but have already come across three in the second chapter that I'm sure I'm doing correctly, but their solutions don't make sense. Seeing as how I'm still pretty rusty, I wanted to be sure that the mistake isn't on my end before I go on to learning more concepts. Here are the three, in particular, that I'm wondering about. Write the solution for 5-2x>4 in interval notation. My answer: (-infinity, 1/2) Their answer: (1/2, infinity) I don't even know how they came up with their answer. Mine was reached by: 5 - 2x > 4 - 2x > -1 x < 1/2 Graph [-5,2) on a number line. My answer was a solid circle at -5 connecting to an open circle at 2. Their answer was an open circle at -5 connecting to an open circle at 2. I was operating under the impression that the closed interval was notated by a solid circle. Then there was a problem involving the solution of x^3 - 5x > 4x^2 Their solution began by adding 4x^2 to the left side of the inequality. Thus, their answer was completely different from mine, because they were factoring x (x^2 + 4x - 5), while I was factoring x (x^2 - 4x -5) . So, I guess I was looking for either validation, or someone to tell me I need to go back and study my algebra a little harder before I tackle pre-calc. Either way, any help would be appreciated. |
||
|
|
pskinner
Joined: Apr 2, 2005 Posts: 694 Status: Offline |
In each case, your analysis is correct, and your methods are on target. I guess it's time to toss that book since it has errors. ---------------------------------------- Principal Skinner |
||
|
| [Show Thread Printable Version] [Post new Thread] |
Re: Is it my textbook, or is it me?