# `-y^2=18x` Graph the equation. Identify the focus, directrix, and axis of symmetry of the parabola.

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Expert Answers

tiburtius | Certified Educator

Let `y^2=4px` be equation of parabola. Then equation of directrix is `x=-p` coordinates of focus are `(p,0)` and axis of symmetry is `x`-axis.

In this case equation of parabola is

`-y^2=18x`

Multiply whole equation by `-1.`

`y^2=-18x`

Therefore,

`4p=-18`

`p=-9/2`

**Directrix is line `x=9/2` focus is point `(-9/2,0)` and axis pf symmetry is `x`-axis.**

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