In Exercises 11–18, determine whether the equation represents y as a function of x. We are looking for y = a bunch of stuff with x on this side. 12. x^2 − y = 9 14. y = sqrt{x + 5} 16. | y | = 4 - x 18. x - 1 = 0 Let me see. For (12), isolating y, I get y = x^2 - 9. I say the equation represents y as a function of x. For (14), This equation clearly shows y as a function of x. I am not too sure about 16. The | y | throws me into a loop. For (18), after adding 1 to both sides, I get x = 1, which is a vertical line going through the point (1, 0). The line x = 1 does not represent y as a function of x. You say?