I don't understand question c and d. Is c really just asking |x| <= 3? In the back of the book it says the answer for (c) "vertical strip consisting of all (x, y) such that -3<= x <= 3, -∞ <= y <= ∞.

For (d) I'm completely lost. Can anyone help me with these two?

NOTE: This is actually from Coddington's ODE's book. I didn't know if I should post this in the Precalculus or Differential Equations section.