A community for students. Sign up today!
Here's the question you clicked on:
 0 viewing
 one year ago
Ok. I have a very hard question. Hopefully someone here can solve it. Now for binary operations, well I have one here, and I need to know if there exists in R (the set of real numbers), an identity element for the operation *. Here is the operation, x*y=abs(xy). Now when I do it, I break up the absolute value into xe for xe greater than 0 and (xe) for xe less than 0, where e is the identity element. Please explain your steps to this problem.
 one year ago
Ok. I have a very hard question. Hopefully someone here can solve it. Now for binary operations, well I have one here, and I need to know if there exists in R (the set of real numbers), an identity element for the operation *. Here is the operation, x*y=abs(xy). Now when I do it, I break up the absolute value into xe for xe greater than 0 and (xe) for xe less than 0, where e is the identity element. Please explain your steps to this problem.

This Question is Closed

ryan16
 one year ago
Best ResponseYou've already chosen the best response.0The identity element is 0

corey1234
 one year ago
Best ResponseYou've already chosen the best response.0No. Only if you restrict the domain to positive real numbers.

Stiwan
 one year ago
Best ResponseYou've already chosen the best response.0I dont get why you're not satisfied with 0. The absolute value of x0 as well as the absolute value of x+0 is x. It doesn't matter whether x is positive or negative, this always holds. Hence x*e = e*x = x for e = 0, and 0 clearly is the identity element.

ryan16
 one year ago
Best ResponseYou've already chosen the best response.0This operation has identity zero if the domain is nonnegative R, and no identity in general if domain is all R. Because abs(x0)=abs(0x)=x (if x<0) which doesnt equal x

corey1234
 one year ago
Best ResponseYou've already chosen the best response.0Yes. Ryan got it right. That is correct.

jickso
 one year ago
Best ResponseYou've already chosen the best response.0Well, it's much easier to see that with a concrete counterexample, am I not right? Let's see, now, exempli gratia, take x=5. Let us suppose that e=0. Then, x * e = 5 * 0 =  5  0  = 5 = 5 =/= 5. To make things more clear, logicaly... You can break down absolute value into three parts, one for x>0, second for x=0 and third for x<0 (of course, we observe R as the set on which the binary operation is defined). This is a disjunction, therefore if we were to conclude anything from it by deduction, we must obtain the same result for every branch, yet we do not: 1) x>0: xe=x > e=0 2) x=0: 0e=0 > e=0 3) x<0: xe=x > e=2x Now, we do not get the same conclusion for every member of disjunction, therefore we can only conclude that it is either e=0 or e=2x. But can we talk about e=2x at all? No, because it is not the condition for a neutral element that "for every x exists e" (in this case we would also be able to restrict it to x<0), but that "exists e such that for every x", and there is a big difference. Note that the condition for the inverse elements is similar to the first case "for every x there exists x"... Conclusion, neutral element would exist on the set of nonnegative real numbers.
Ask your own question
Ask a QuestionFind more explanations on OpenStudy
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.