Thomas' Calculus 13th Edition

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

Appendices - Section A.3 - Lines, Circles, and Parabolas - Exercises A.3 - Page AP-18: 38

Answer

Intersection points: $(\displaystyle \frac{1-\sqrt{5}}{2},\frac{3-\sqrt{5}}{2})$ and $(\displaystyle \frac{1+\sqrt{5}}{2},\frac{3+\sqrt{5}}{2})$ .

Work Step by Step

See attached image (desmos.com). To find the intersection points algebraically, substitute $y=1+x $ into the second equation: $(1+x)=x^{2}$ $0=x^{2}-x-1$ $x=\displaystyle \frac{-(-1)\pm\sqrt{1-4(1)(-1)}}{2(1)}$ $ x=\displaystyle \frac{1\pm\sqrt{5}}{2}\qquad$... $ \displaystyle \frac{1+\sqrt{5}}{2}\approx 1.618,\quad \frac{1-\sqrt{5}}{2}\approx-0.618,$ Back-substitute: $x=\displaystyle \frac{1+\sqrt{5}}{2}\quad \Rightarrow\quad y= \frac{1+\sqrt{5}}{2}+1=\frac{3+\sqrt{5}}{2}\approx 2.618$ $x=\displaystyle \frac{1-\sqrt{5}}{2}\quad \Rightarrow\quad y= \frac{1-\sqrt{5}}{2}+1=\frac{3-\sqrt{5}}{2}\approx 0.382$ Intersection points: $(\displaystyle \frac{1-\sqrt{5}}{2},\frac{3-\sqrt{5}}{2})$ and $(\displaystyle \frac{1+\sqrt{5}}{2},\frac{3+\sqrt{5}}{2})$
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