Up to 10 miles in any direction means within a circle of radius 10 centered at (4,-9).
[tex](x,y) \textrm{ where } (x-4)^2 + (y+9)^2 \le 100[/tex]
Answer: (x-4)^2+(y+9)^2=10^2
Explanation: The circle in the problem takes the form (x-h)^2+ (y-k)^2=r^2. The hiker started at the center of the circle (h,k) = (4,9). The radius of the circle= 12. When you plug these values in you get (x-4)^2+ ky+9)^2=10^2
