\[\sqrt{- 2x^{2} + 5x + 2}\]
\[- 2x^{2} + 5x + 2 \geq 0\]
\[2x^{2} - 5x - 2 \leq 0\]
\[D = 25 + 16 = 41\]
\[x_{1} = \frac{5 + \sqrt{41}}{4};\]
\[x_{2} = \frac{5 - \sqrt{41}}{4}.\]
\[\frac{5 - \sqrt{41}}{4} \leq x \leq \frac{5 + \sqrt{41}}{4}.\]