Precalculus · Problem 1.1.30

You're looking for points on a horizontal line where $y = -1$, and you need them to be exactly 4 units away from a fixed point. The key is the distance formula: the distance between any two points is $\sqrt{(x_2-x_1)^2 + (y_2-y_1)^2}$. Since you know the $y$-coordinate is always $-1$, the distance becomes an equation in just $x$ that you can solve.

You're looking for points on a horizontal line where $y = -1$, and you need them to be exactly 4 units away from a fixed point. The key is the distance formula: the distance between any two points is $\sqrt{(x_2-x_1)^2 + (y_2-y_1)^2}$. Since you know the $y$-coordinate is always $-1$, the distance becomes an equation in just $x$ that you can solve.