• 268[ 1, 2, 3, 6, 8].

Here are the equivalent exercises for those using the First Edition:

• 243[ 4, 5], 256[8]
• Sketch a graph of the set

  {(x,y) : x² + y² ≤ 1, (x-2)² + y² < 2},

  and describe whether this set is relatively open, or relatively closed in the closed unit ball (B₁(0,0))^-. Do the same for the open ball of radius square root of two B_{√ 2}(2,0). Explain your answers.