(a) Let a > 0 be a constant. Find all critical points of f (x) = x + a√x.
This is my work so far
-1 = (a/2)(1/sqrt(x))
I calculated the Critical point as x=a/4
(b) Use derivatives to show that f is increasing and its graph is concave down for all x > 0.
Not sure how to do this part.