My Math Forum  

Go Back   My Math Forum > High School Math Forum > Algebra

Algebra Pre-Algebra and Basic Algebra Math Forum


Reply
 
LinkBack Thread Tools Display Modes
April 25th, 2013, 10:33 AM   #1
Senior Member
 
Joined: Apr 2013
From: Ramallah, Palestine

Posts: 349
Thanks: 0

Find the Domain of the Function.

Find the domain of the function

#33. cuberoot. of 2t-1

so do I say 2t - 1 = 0
then 2t = 1
then t = 1/2 making the domain (-infinity, 1/2)


is this correct?

#35.
1 / 4th root of x^2 -5x
so I factored and got
x(x-5)
then I got x = 0 and x = 5
then I got D= (-inf, 0)Union(5,infinity)
is that right?
Shamieh is offline  
 
April 25th, 2013, 10:54 AM   #2
Math Team
 
Joined: Sep 2007

Posts: 2,409
Thanks: 6

Re: Find the Domain of the Function.

Quote:
Originally Posted by Shamieh
Find the domain of the function

#33. cuberoot. of 2t-1

so do I say 2t - 1 = 0
then 2t = 1
then t = 1/2 making the domain (-infinity, 1/2)


is this correct?
Why did you do that? If it were a squareroot, then you recall that you cannot take a (real number) root of a negative number so the argument (the "2t- 1" here) must be non-negative. But that does NOT apply to cube roots.

Quote:
#35.
1 / 4th root of x^2 -5x
so I factored and got
x(x-5)
then I got x = 0 and x = 5
then I got D= (-inf, 0)Union(5,infinity)
is that right?
Yes, it is. The product of two negative numbers (x< 0 so both x and x- 5 are negative) or two positive numbers (x> 5 so both x and x- 5 are positive) is positive so you can take the fourth root. But I hope you understand that is required for even roots, not odd roots!
HallsofIvy is offline  
April 25th, 2013, 11:35 AM   #3
Senior Member
 
Joined: Apr 2013
From: Ramallah, Palestine

Posts: 349
Thanks: 0

Re: Find the Domain of the Function.

Quote:
Why did you do that? If it were a squareroot, then you recall that you cannot take a (real number) root of a negative number so the argument (the "2t- 1" here) must be non-negative. But that does NOT apply to cube roots.
Yeah, so you are saying the first one I don't need to set it to zero because it is even so it is just all REAL #s right? or [neg inf to infinity]?
Shamieh is offline  
April 30th, 2013, 09:55 AM   #4
Senior Member
 
Joined: Apr 2013
From: Ramallah, Palestine

Posts: 349
Thanks: 0

Re: Find the Domain of the Function.

?
Shamieh is offline  
April 30th, 2013, 08:59 PM   #5
Global Moderator
 
Joined: Dec 2006

Posts: 18,060
Thanks: 1396

It's a reasonable guess that these questions are about real functions of a real variable, so the domain will be some subset of the reals, such as all the reals (which is what (-infinity, infinity) amounts to).
skipjack is offline  
Reply

  My Math Forum > High School Math Forum > Algebra

Tags
domain, find, function



Search tags for this page
Click on a term to search for related topics.
Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Find the Domain of the Function #3 Shamieh Algebra 2 July 1st, 2013 11:27 PM
Find the Domain of each Function Shamieh Algebra 3 July 1st, 2013 02:27 PM
How do I find the domain for this function? daigo Algebra 1 February 22nd, 2012 08:56 PM
find the domain of the function rodjav305 Algebra 2 July 9th, 2009 09:18 AM
Find the Domain of the Function. Shamieh Calculus 3 December 31st, 1969 04:00 PM





Copyright © 2017 My Math Forum. All rights reserved.