Differential Equations and Linear Algebra (4th Edition)

Published by Pearson
ISBN 10: 0-32196-467-5
ISBN 13: 978-0-32196-467-0

Chapter 5 - Inner Product Spaces - 5.5 Chapter Review - Additional Problems - Page 377: 14

Answer

$d=\frac{142}{\sqrt 430}$

Work Step by Step

We need to find plane $P$ first: $P=\{a.v+b.w\}: a,b \in R$ Substituting: $P=\{a.(-1,0,5)+b.(3,2,-1)\\ =\{(-a,0,5a)+(3b,2b,-b)\}\\ =\{(-a+3b,2b,5a-b)\}$ Thus: $x=-a+3b\\ y=2b\\ z=5a-b$ From the first equation, we obtain: $a=y-x\\ b=\frac{y}{3}$ Substituting to the third equation: $z=5(y-x)-\frac{y}{3}\\ \rightarrow 15x-14y+3z=0$ Hence, the equation of plane $P$ formed by $v$ and $w$ is: $15x-14y+3z=0$ Using the formula from Exercise 28, the distance of a point $P(x_0,y_0,z_0)$ to the plane $P..ax+by+cz+d=0$ is given by: $$d(P,P)=\frac{|x_0.a+y_0.b+z_0.c+d|}{\sqrt a^2+b^2+c^2} \\ =\frac{(-2).15+8.(-14)+0.3+0}{\sqrt 15^2+(-14)^2+3^2}\\ = \frac{|142|}{\sqrt 225+196+9}\\ =\frac{142}{\sqrt 430}$$ Hence, $d=\frac{142}{\sqrt 430}$
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