3. Recall that critical points occur where $f'(x) = 0$ or where $f'(x)$ is undefined. Let $f(x) = x + a\sqrt{x}$ where $a$ is some positive constant. (a) Set $f'(x) = 0$. Show why this can't happen. (b) What is the only critical point of $f(x)$? (c) Show that $f$ will always be increasing for $x > 0$. (d) Show that $f$ will always be concave down for $x > 0$.
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