Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 10 - Analytic Geometry - 10.1 Parabolas - 10.1 Exercises - Page 966: 4

Answer

Vertex: $(-3,4)$ Foci: $(0,4)$ Directrix: $x=-3$ Axis of symmetry: $x$ Domain of the parabola:$[-3,\infty ]$ Range of the parabola: $[-\infty,\infty ]$

Work Step by Step

The first thing we see is that the equation has the form: $$(y-k)^2=4p(x-h)$$ where the vertex is $$(h,k)$$ This means the parabola opens left or right, and has axis of symmetry of $x$ and the directrix $x=-p$, so let's find $p$. If we match the equations we find: $(y-4)^2=12(x+3)$ $4p=12$ $p=\frac{12}{4}=3$ $k=-(-4)=4$ $h=-(3)=-3$ So the vertex is: $(-3,4)$, and the directrix: $y=-p$ $y=-3$ In order to find the foci, we know that the foci is in the same axis as the vertex and is $p$ units away of it, so: Foci $(h+p,p)$ Foci $(-3+3,4)$ Foci $(0,4)$ To obtain the domain and the range of the parabola we see from the graph, $y$ can take any value so, it goes from $-\infty$ to $\infty$ this is the range. For the domain: we know the vertex is the biggest or the smallest value of the parabola, so this means all values start from there, so from $-3$ to $\infty $.
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