Answer:3.46 km
Step-by-step explanation:
Given
shape of hill [tex]y=-2(x-3)^2+6[/tex]
at the bottom y=0 i.e.
[tex]0=-2(x-3)^2+6\\(x-3)^2=3\\x-3=\pm\sqrt{3}\\x=3\pm\sqrt{3}[/tex]
width of the bottom
[tex]3+\sqrt{3}-[3-\sqrt{3}]=2\sqrt{3}\ km\ or\ 3.46\ km[/tex]
