Chapter 4 - Exponential and Logarithmic Functions - Section 4.1 Composite Functions - 4.1 Assess Your Understanding - Page 281: 85

$\frac{1}{4},4$.

Step 1. Let $u=\sqrt x$, for $f(x)=0$, we have $2u^2-5u+2=0 \Longrightarrow (2u-1)(u-2)=0 \Longrightarrow u=\frac{1}{2},2$ Step 2. For $u=\frac{1}{2}$, we have $\sqrt x=\frac{1}{2}$, thus $x=\frac{1}{4}$. Step 3. For $u=2$, we have $\sqrt x=2$, thus $x=4$.