This is the definition of continuity. And they tell us that f of 5, when x equals 5, the value of the function is equal to c. So this must be equal to c. So what we really need to do is figure out what the limit of f of x as x approaches 5 actually is. Now if we just try to substitute 5 into the expression right up here, in the numerator you have 5 plus 4 is 9, the square root of that is positive 3, the principal root is positive 3, 3 minus 3 is 0, so you get a 0 in the numerator, and then you get 5 minus 5 in the denominator, so you get 0 in the denominator. So you get this indeterminate form of 0 over 0. And in the future we will see that we do have a tool that allows us, or gives us an option to attempt to find limits when we get this indeterminate form. It's called L'Hopital's Rule. But we can actually tackle this with a little bit of fancy algebra.