Events & Promotions
|
|
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized
for You
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Apr 2512:30 AM EDT
-01:30 AM EDT
At one point, she believed GMAT wasn’t for her. After scoring 595, self-doubt crept in and she questioned her potential. But instead of quitting, she made the right strategic changes. The result? A remarkable comeback to 695. Check out how Saakshi did it.
Apr 2610:00 AM EDT
-11:00 AM EDT
The Target Test Prep course represents a quantum leap forward in GMAT preparation, a radical reinterpretation of the way that students should study. Try before you buy with a 5-day, full-access trial of the course for FREE!
Apr 2711:00 AM EDT
-12:00 PM EDT
Prefer video-based learning? The Target Test Prep OnDemand course is a one-of-a-kind video masterclass featuring 400 hours of lecture-style teaching by Scott Woodbury-Stewart, founder of Target Test Prep and one of the most accomplished GMAT instructors
Apr 2808:00 AM PDT
-11:00 AM PDT
Whether you are just beginning your MBA journey or fine-tuning your path to a 700+ score, GMAT Day is designed to give you a competitive edge.
19 Dec 2009, 02:01
Kudos
Bookmarks
Hi guys
Need to know how to solve multiple modulus inequalities
Ex - Solve |x-10| - |2x+3| <= |5x-10|
I do understand that we need to first find the roots, which happen to be 10, -3/2 and 2 in this case
we can then divide them into intervals -
x<-3/2
-3/2<x<2
2<x<10
x>10
what do we do post this division into intervals?
Need to know how to solve multiple modulus inequalities
Ex - Solve |x-10| - |2x+3| <= |5x-10|
I do understand that we need to first find the roots, which happen to be 10, -3/2 and 2 in this case
we can then divide them into intervals -
x<-3/2
-3/2<x<2
2<x<10
x>10
what do we do post this division into intervals?
Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Quantitative Questions Forum
Still interested in this question? Check out the "Best Topics" block below for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
19 Dec 2009, 03:47
Kudos
Bookmarks
zaarathelab
If we dot he way you are proposing:
Yes, there are 3 check point at which absolute values in the example change their sign: -3/2, 2, and 10 (te values of x for which the expression in || equals to zero). Then you should expand the modulus in these ranges:
A. \(x<-\frac{3}{2}\) --> \(|x-10|-|2x+3|\leq{|5x-10|}\) --> \(-(x-10)+(2x+3)\leq{-(5x-10)}\) --> \(6x\leq{-3}\) --> \(x\leq{-\frac{1}{2}\) --> as we considering the range when \(x<-\frac{3}{2}\), then finally we should write \(x<-\frac{3}{2}\):
----(\(-\frac{3}{2}\))---------------------------------
B. \(-\frac{3}{2}\leq{x}\leq{2}\) --> \(-(x-10)-(2x+3)\leq{-(5x10)}\) --> \(2x<=3\) --> \(x<={\frac{3}{2}\) --> \({-\frac{3}{2}}\leq{x}\leq{\frac{3}{2}}\);
----(\(-\frac{3}{2}\))----(\(\frac{3}{2}\))-------------------------
C. \(2<x<10\) --> \(-(x-10)-(2x+3)\leq{5x-10}\) --> \(17\leq{8x}\) --> \(x\geq{\frac{17}{8}}\) --> \({\frac{17}{8}}\leq{x}<10\);
---------------------(\(\frac{17}{8}\))--------(\(10\))----
D. \(x\geq{10}\) --> \((x-10)-(2x+3)\leq{5x-10}\) --> \(-3\leq{6x\) --> \(x\geq{-\frac{1}{2}}\) --> \(x\geq{10}\);
---------------------(\(\frac{17}{8}\))--------(\(10\))----
After combining the ranges we've got, we can conclude that the ranges in which the given inequality holds true are:
\(x\leq{\frac{3}{2}}\) and \({\frac{17}{8}}\leq{x}\)
----(\(-\frac{3}{2}\))----(\(\frac{3}{2}\))----(\(\frac{17}{8}\))--------(\(10\))-----
One important detail when you define the critical points (10, -3/2 and 2) you should include them in either of intervals you check. So when you wrote:
x<-3/2
-3/2<x<2
2<x<10
x>10
You should put equal sign for each of the critical point in either interval. For example:
x=<-3/2
-3/2<x<=2
2<x<1=0
x>10
Notice, that in solution I put the equal sign in different way, but it doesn't matter. It's important just to consider the cases when x equals to the critical points and include them when expanding given inequality.
01 Feb 2012, 02:31
Kudos
Bookmarks
Could somebody explain this in detail, please?
I didn't get the concept of roots here, it doesn't make the equation zero - isn't it?
I didn't get the concept of roots here, it doesn't make the equation zero - isn't it?
