I'll explain the first question. You have (is that right ? There is confusion in your question, is it the whole fraction under square root ?) :

Now you want to find the domain of this function. That is, for which values of is defined.

- look out for any special operations that are not defined for all real numbers (for example, is defined for any real number, but is not defined for negative numbers).Step 1

Here, you have two such operations : the square root cannot take any negative number, and the denominator of the fraction cannot be equal to .

- identify the expressions that may lead to an undefined function.Step 2

First issue, the square root : cannot be negative, so it must be positive or equal to . Thus, we have :

Second issue, the denominator, which is , cannot be zero. Thus, we have :

- put together the information and extract the domain.Step 3

Remind the information found :

Therefore, the domain of would be :

- check your answer on a graph-drawer software (or your calculator). Ensure the domain you found matches the one found by the software, and be sure you put the right interval signs ( [,],(,) ), especially on a zero-denominator restriction (be sure to exclude it on BOTH sides of the interval).Step 4

Does it help ?

PS : if I misunderstood your equation, I made sure I gave you enough tips for you to be able to work out the domain by yourself following the 4 steps.