Expert: Steve Holleran - 9/10/2007

Question
I realize this might be easy for you but I am having a hard time in this class. Could you help with this problem and others?      f(x)=sqrt x-8  there is a sign around the x-8 that looks like a check mark and division sign.

Answer
Hi Jeffrey,

Okay, the sign you describe is indeed the square root sign.

So the function you have is sqrt(x - 8).

Now, the stuff inside the square root must be zero or positive, that is :

              x - 8 >= 0    (greater than or = to 0)

So, adding 8, the domain is x >= 8.  You can use what's called interval notation to write this as [8, inf).  

( The bracket indicates that you want to include the 8.  If you didn't, you would use a left parenthesis, like this:

               (8,inf).

So, in the future, if you come across other sqrt functions , just remember that the stuff inside the sqrt must be >=0.

Hope this helps.
Steve Holleran