Thomas' Calculus 13th Edition

Published by Pearson
ISBN 10: 0-32187-896-5
ISBN 13: 978-0-32187-896-0

Chapter 11: Parametric Equations and Polar Coordinates - Section 11.6 - Conic Sections - Exercises 11.6 - Page 678: 45

Answer

$(y+3)^{2}=4(x+2)$ New focus: $\quad (-1, -3)$ New directrix: $\quad x=-3$ New vertex:$ \quad (-2,-3)$

Work Step by Step

Shift left by 2 $\Rightarrow$ in the equation, replace $x$ with $x+2$. Shift down by 3 $\Rightarrow$ in the equation, replace $y$ with $y+3$. The new equation is: $\quad (y+3)^{2}=4(x+2)$ $y^{2}=4x\quad $ Which is of the form $y^{2}=4px $ ,$\qquad x=\displaystyle \frac{y^{2}}{4p}$ ,$\qquad$... opens right, $p=1$ focus: $\quad(p,0)$= $\quad(1,0)$ directrix: $ x=-p\Rightarrow \quad x=-1$ vertex:$\quad (0,0)$ The translations are such that $(x,y)\rightarrow(x',y')$, where $\left\{\begin{array}{ll} x'=x-2 & \text{... shift left}\\ y'=y-3 & \text{... shift down} \end{array}\right.$ New focus: $\quad(1-2,0-3) = (-1, -3)$ New directrix: $ x=-1-2\Rightarrow \quad x=-3$ New vertex:$\quad (0-2,0-3) = (-2,-3)$
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