Part 1: The general form for this matches y^2 = -4cx, which implies that this opens to the left. (Imagine assigning any value of y, whether positive or negative, which would result in a positive left-hand value. Then to match this sign, the value of x must be negative so that the right-hand side becomes positive as well.)
Part 2: The distance from the vertex to the directrix is given by c. This equation has its vertex at the origin (0, 0). If it opens to the left, the directrix is a vertical line to the right of the origin. This equation is y^2 = -4(1/2)x, so c = 1/2, and the directrix has the equation x = 1/2.
Part 3: The focus is inside the parabola, but it is the same distance from the vertex as the directrix. This distance is 1/2 units, and it will be to the left of the vertex. So the focus is at (-1/2, 0).
By changing the number into a decimal, and then moving the decimal twice to the right.
-15 and -2 don’t make +17
The equation of a circle is (x - h)² + (y - k)² = radius² where (h, k) is the ordered pair for the center.
(x - (- 3))² + (y - 6)² = 10²
(x + 3)² + (y - 6) = 100
