Question about Implicit Differentiation.

I'm given the question:

"Find (dy/dx) for each of the following in terms of x and y using implicit differentiation."

sqroot(x) + sqroot(y) = 5

This is what I have so far...

sqroot(x) + sqroot(y) = 5

y=(5-sqroot(x))^2

y'=2(5-sqroot(x))(-x^(-1/2))

y'=2(5-sqroot(x))(-1/sqroot(x))

Am I headed in the right direction? If not, can someone show me where I should be heading? My teacher (unfortunately) didn't do a very good job explaining things...

Thanks. :)

EDIT: Sorry, this is all wrong. I solved the problem though. :)