Function problem

It has to be D, I believe.

Don't take my word on this (I'm no math guru), but you might as well plug in numbers for this one. I don't believe you can have a square root of a negative number. Therefore, by plugging into x various numbers you can think of, you want to make sure the resulting sum under the square root is not negative.

It seems that the only answer choice for x that wouldn't result in a negative sum (under the square root) would be 2. And since x is a possible number in your domain, 2 is your answer (domain in this case means a value of x, i believe).

I hope this helps, and if I am wrong, then please correct me.

Oh, and it can't be E because then the result on the denominator is zero, and you can't have that.

That's long compared to what the question requires but it will perhaps explain it to you more concretely.

You need what is in the square root to be 0 or positive.
If you take x=2 or x<2 it is ok because numerator and denumerator are negative so it gives you a positive result.
If we want both numerator and denumerator to be positive, we need x to be at least equal to 8 (7 is impossible given x-7 at the denumerator).
So you can draw this line:
-------------2--------------7-----8---------------

x must be: x<=2 and x>=8

You are right, I didn't check well the different possible answers, I would have seen it...

hi Ian

I understood the discussion , but i would like to know wat exactly he word " Domain" means in context of value F(x) given here ??

I just didnt get that part :

Vishu

vishubn wrote:hi Ian

I understood the discussion , but i would like to know wat exactly he word " Domain" means in context of value F(x) given here ??

I just didnt get that part :

Vishu

The domain of a function of x (i.e. f(x)) is all the possible values of x.

On most GMAT questions, the domain is specified in the question itself. For example:

For all positive integers x, f(x) = 3(rootx) + 6

has a domain of all positive integers.

"In the domain of the function" just means a possible value for x. So the question could have read,

If F(x)= root(x-2)/(x-7), which of the following is a possible value of x?

That's very good explanation. I understand Domain now much better.