# Chapter 9 - Section 9.3 - The Parabola - Exercise Set - Page 997: 69

The light bulb must be placed at 1 inch above the vertex.

#### Work Step by Step

As per the given statement , we have $y=1$ and Diameter = 4 inches. This implies that Radius: $2x=4 \implies x=2$ Now, consider $x^2=4py$ This implies that $(2)^2=(4p)(1) \implies p=1$ Hence, the light bulb must be placed at 1 inch above the vertex.

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