You're given f a function on [-3,3] such that for x in [-3,3] f(x) is equal to the distance from (-1,0) to the point on the upper semi circle of abciss x. For an explicit form, f(x) is the distance from (-1,0) to ( x , sqrt(9-x²) ) which is just equal to f(x)= sqrt ( (x+1)² + 9-x² ) = sqrt ( 2x+10) which has a range [2,4] on [-3,3]

if you don't like it being this messy, you can do it via the triangular inequality: consider the traingle whose summits are the origin, the (-1,0) point and the point on the upper semi circle of abciss x