Chapter 1 - Functions and Limits - 1.1 Four Ways to Represent a Function - 1.1 Exercises - Page 21: 53

$y=1-\sqrt{-x}$ With domain: $x\leq0$

We need to solve the equation for $y$: $x+(y-1)^2=0$ $(y-1)^2=-x$ $y-1=\pm\sqrt{-x}$ $y=1\pm\sqrt{-x}$ Since we need the bottom half of the parabola, we use: $y=1-\sqrt{-x}$ With domain: $x\leq0$