Differential Equations and Linear Algebra (4th Edition)

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

Chapter 8 - Linear Differential Equations of Order n - 8.10 Chapter Review - Additional Problems - Page 576: 66

Answer

See below

Work Step by Step

Given: $y''-8y'+17y=e^{4x}\csc x$ In this case the substitution $y(x) = x^r$ yields the indicial equation $r^2-8r+17=0$ Solve the equation $r_1=4+i\\ r_2=4-i$ It follows that two linearly independent solutions to the given differential equation are $y_1(x)=e^{4x}\sin x\\ y_2(x)=e^{4x}\cos x$ so that the particular solution is $y(x)=u_1e^{4x}\sin x+u_2e^{4x}\cos x$ We first compute the appropriate derivatives $0=u_1'(x)e^{4x}\sin x+u_2'(x)e^{4x}\cos x\\ e^{4x}\csc x=u_1'(x)(e^{4x}\sin x)'+u_2'(x)(e^{4x}\cos x)'$ Substituting these expressions into the given equation, we find that $u$ must satisfy $u_1'=\cot x\\ u_1=\ln (\sin x)$ and $u_2'=-1\\ u_2=-x$ Hence, the general solution is: $y(x)=e^{4x}\sin\ln (\sin x)-e^{4x}x\cos x$
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