AllExperts > Calculus 
Search      
Calculus
Volunteer
Answers to thousands of questions
 Home · More Calculus Questions · Answer Library  · Encyclopedia ·
More Calculus Answers
Question Library

Ask a question about Calculus
Volunteer
Experts of the Month
Expert Login

Awards

About Us
Tell friends
Link to Us
Disclaimer

 
 
 
 
About Scotto
Expertise
Any kind of mathematics (calculus, analysis, game theory, linear approximation, finite differences, linear regression, linear programming, numerical analysis, probability, statistics, etc.). I also have answered some questions in Physics (mass, momentum, falling bodies), Chemistry (charge, reactions, symbols, molecules), and Biology.

Experience
Experience in the area: I have tutored students in all areas of mathematics for over 20 years. Education/Credentials: BSand MS in Mathematics from Oregon State University, where I completed sophomore course in Physics and Chemistry. I received both degrees with high honors. Awards and Honors: I have passed Actuarial tests 100, 110, and 135.

Publications
Maybe not a publication, but I have respond to well oveer 3000 questions on the PC. That's around 2,000 in basic math and 1,000 in advanced math.

Education/Credentials
I aquired well over 40 hours of upper division courses. This was well over the number that were required. I graduated with honors in both my BS and MS degree from Oregon State University. I was allowed to jump into a few junior level courses my sophomore year.

Awards and Honors
I have been nominated as the expert of the month several times. All of my scores right now are at least a 9.8 average (out of 10).

Past/Present Clients
My past clients have been students at OSU, students at the college in South Seattle, referals from a company, friends and aquantenances, people from my church, and people like you.

 
   

You are here:  Experts > Teens > Homework/Study Tips > Calculus > Inequalities

Calculus - Inequalities


Expert: Scotto - 7/15/2008

Question
QUESTION: 1) f(x)= (2x-3)/(x-5)

What is modulusf(x)modules > (or equal to) 3/2.

I have found the answer of f(x) > (or equal to) 3/2 to be x< (or equal to) -9 or x> 5 and am sure this is correct. However, I am not sure how to solve the qn above.

2) Given a,b are positive constants and a<b, solve for x:

(x-b)/(x-a) > (x-b)/b

Thanks for the help sir :)



ANSWER: For future references, ≥ is alt-242 and ≤ is alt-243.

1) I'm not sure what modulusf(x)modules are.

2) Note that the answer needs x=a generates an error.  IN the langues C, this is referred to as x!=a (x is not equal to a).
The (x-b) can be cancelled of each side.
Inverting, this leaves x-a≥b, or x≥a+b.


---------- FOLLOW-UP ----------

QUESTION: 1) I meant modulus(fx)...

2) the correct answer shld be x<a or b<x<a+b, which I cannot seem to arrive at..

would you be able to help out with these 2 qns again pls..

thanks :)

Answer
Sorry for the error in my answer to 2.  It should have read:
2) Note that the answer needs x=a generates an error.  In the computer language C, this is referred to as x!=a (x is not equal to a).

Now to your current question:
1) When the modulus of a function is taken, it is generally shortened as 'mod'.  An example would be like
7 mod 3 = 1 or
12 mod 5 = 2.

When you are given a mod b, the result is the remainder when dividing a by b.

I still don't know what modulus[f(x)] refers to since there is no term b in the expression.  If it was modulus [f(x),2], that would be the remainder on f(x) when dividing by 2 for each x.

An example would be f(x)=2x and we look at mod[f(x),3].  This would generate a series of lines starting at 0 and going up to 3 on an infinite number of intervals between -∞ and ∞.  They would be ... (-1.5, 0), (0, 1.5), (1.5, 3), (3, 4.5) ... .

2) We are looking at (x-b)/(x-a) > (x-b)/b, a<b.
Depending on the values of a and b, I get different results and can’t arrive at that answer either.

When x>a and b<0, the equation is true.
When x<a and b>0, the equation is true.
When x<a+b with (x<a, b<0), it is true.
When x<a+b with (x>a, b>0), it is true.

I designed the entire problem in a spreadsheet and found it to be true in a variety of places.  The critical lines were b=0 and a=x.  In each of the regions, the function turned out to be all true, all false, or a mixture with cutting lines on diagonals.  I did get it to always be true if a>x.

The rest, though, is more than I can get an answer for right now.


Add to this Answer   Ask a Question


 
User Agreement | Privacy Policy | Kids' Privacy Policy | Help
Copyright  © 2008 About, Inc. AllExperts, AllExperts.com, and About.com are registered trademarks of About, Inc. All rights reserved.