Answer:
See below.
Explanation:
We have the expression:

And we want to determine the domain restrictions of the expression.
Remember that the radicand (expression under the square root) must always be positive or 0. This is because we can't take the square root of a negative (and the square root of 0 is just 0). So, to find the domain restrictions, we can write and solve for the following inequality:

This is saying (8c+4) must be greater than or equal to 0. In other words, it's positive or 0.
So, solve for c. Subtract 4 from both sides:

Now, divide both sides by 8. This yields:

So, our c must be greater than or equal to -1/2. If it is less than -1/2, we won't have a solution.