Consider the quadratic equation $\displaystyle {y}=-{3}{x}^{{2}}-{9}{x}+{54}$.

Determine the following: (enter all numerical answers as integers or decimals. Round your answer to two decimal places as needed.):

The smallest $\displaystyle {x}$-intercept is $\displaystyle {x}=$ .
The largest $\displaystyle {x}$-intercept is $\displaystyle {x}=$ .
The $\displaystyle {y}$-intercept is $\displaystyle {y}=$ .
The vertex is ( , ).
The line of symmetry has the equation .