Be very careful with your signs. And we can also go a bit further in the expansion. I'm assuming that that radical is supposed to be and not as you have written:

.

Start by splitting the fraction:

Now split the factors:

Notice that theentiredenominator ends up getting subtracted. That is, we will have to distribute the -1 to each term on the right side:

Notice also that can be factored as , giving us

And finally, remember that . So, we can convert that radical into a rational exponent:

Now, can you finish it?