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 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?
April 25th, 2013, 10:54 AM   #2
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Re: Find the Domain of the Function.

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 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!

April 25th, 2013, 11:35 AM   #3
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Re: Find the Domain of the Function.

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 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]?

 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. ?
 April 30th, 2013, 08:59 PM #5 Global Moderator   Joined: Dec 2006 Posts: 19,270 Thanks: 1679 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).

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