Find the Limit $L$ For the Given Function $f$ , the Point $x _ { 0 }$

Multiple Choice

Find the limit $L$ for the given function $f$ , the point $x _ { 0 }$ , and the positive number $\varepsilon$ . Then find a number $\delta > 0$ such that, for all $x _ { t } 0 < \left| x - x _ { 0 } \right| < \delta \Rightarrow | f ( x ) - L | < \varepsilon$ .
- $f ( x ) = \sqrt { 18 - x } , L = 4 , x _ { 0 } = 2 , \text { and } \varepsilon = 1$

A) -9
B) 9
C) 7
D) 12