Abigail H.

asked • 03/15/18

what is the domain of y=3\x-9

need help 

2 Answers By Expert Tutors

By:

Roger N. answered • 03/15/18

Tutor
4.9 (292)

. BE in Civil Engineering . Senior Structural/Civil Engineer

About this tutor ›
About this tutor ›
what is the domain of y=3\x-9
 
The domain of this fraction is in he denominator where x-9 should not equal 0. The domain is therefore all real numbers excluding 9 because x-9 =0, x=9 The domain can be written as [-∞,9) and (9,+∞]
Upvote • 0 Downvote
More
Report

Kenneth S.

Roger, you are correct except you may not use square bracket to indicate exact endpoint of an interval at an infinity, because a square bracket means INCLUDING THIS EXACT endpoint.  Infinity is not a specific exact Real number.
 
It should also be noted that the wrong division symbol was written by the student, and also that the binomial denominator NEEDED to be enclosed in parentheses.
Report

03/15/18

Arturo O.

As worded, the problem was literally asking for the domain of
 
3/x - 9,
 
which is all real numbers except x = 0.  I sent WyzAnt a long communication just last night about the need to instruct students to correctly upload equations with proper grouping of expressions.  It was not the first time, and I am sure other tutors have written WyzAnt about this.
Report

03/15/18

Roger N.

tutor
yes Kenneth. I knew that but I used open interval symbol for 9 which is not in the domain. My thought was if I used open interval for infinity it would also mean that infinity is not included in the domain. which it is. Two school of thoughts here..
Report

03/16/18

Still looking for help? Get the right answer, fast.

Ask a question for free

Get a free answer to a quick problem.
Most questions answered within 4 hours.

OR

Find an Online Tutor Now

Choose an expert and meet online. No packages or subscriptions, pay only for the time you need.