Consider the quadratic function f(x)=x23x+18\displaystyle {f{{\left({x}\right)}}}=-{x}^{{2}}-{3}{x}+{18}.

Determine the following:

The smallest x\displaystyle {x}-intercept is x=\displaystyle {x}=  
The largest x\displaystyle {x}-intercept is x=\displaystyle {x}=  
The y\displaystyle {y}-intercept is y=\displaystyle {y}=