1/4(y+3)=(x-2)^2 what is the directirx

To make this as easy as possible, we will find the vertex from the equation above.  The vertex is sitting at (h, k) of (2, -3).  The directrix is the same number of units from the vertex that the focus is.  The formula for the focus for an upwards-opening parabola is .  The "a" in that formula is the 1/4 sitting in front of (y+3).  Filling in accordingly, we have .  Simplifying we get .  The focus is on the axis of symmetry along with the vertex, and is 1 unit above the vertex. That means that the directrix is 1 unit BELOW the vertex and is a horizontal line.  Therefore, the directrix has an equation of y = -4

The answer is option c.

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