Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 11 - Section 11.4 - Shifted Conics - 11.4 Exercises - Page 814: 19

Answer

(a) Vertex: $V(2,3)$ Focus: $F(5,3)$ Directrix: $x=-1$ (b)

Work Step by Step

Equation of a parabola with horizontal axis and vertex at $(h,k)$: $(y-k)^2=4p(x-h)$ $y^2-6y-12x+33=0$ $y^2-6y+9=12x-33+9=12x-24$ $(y-3)^2=12(x-2)$ $h=2$ $k=3$ Vertex: $V(2,3)$ $4p=12$ $p=3$. Parabola opens to the right. The given equation can be obtained by shifting $y^2=12x$ right 2 units and upwnward 3 units: Focus: $F(p,0)=F(3,0)$ Directrix: $x=-p=-3$ Now, shift the vertex and the directrix $2$ unit to the right and 3 units upwnward: Focus: $F(5,3)$ Directrix: $x=-1$
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