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Fundamentals Of Differential Equations And Boundary Value Problems
Found in: Page 180
Fundamentals Of Differential Equations And Boundary Value Problems

Fundamentals Of Differential Equations And Boundary Value Problems

Book edition 9th
Author(s) R. Kent Nagle, Edward B. Saff, Arthur David Snider
Pages 616 pages
ISBN 9780321977069

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Short Answer

Determine the form of a particular solution for the differential equation. (Do not evaluate coefficients.) y''-6y'+9y=5t6e3t

The particular solution is:

yp(x)=(A6t8+A5t7+A4t6+A3t5+A2t4+A1t3+A0t2)e3t

See the step by step solution

Step by Step Solution

Step 1: Use the method of undetermined coefficients to find a particular solution of given differential equation.

The given differential equation is in the form of;

ax''+bx'+cx=ert

To find a particular solution to the differential equation

ay''(x)+by'(x)+cy(x)=Ctmert

Where m is a nonnegative integer, use the form;

yp(x)=ts(Amtm+...+A1t+A0)ert

  1. s = 0 if r is not a root of the associated auxiliary equation;
  2. s = 1 if r is a simple root of the associated auxiliary equation;
  3. s = 2 if r is a double root of the associated auxiliary equation.

Step 2: Now, write the auxiliary equation of the above differential equation

The given differential equation is,

y''-6y'+9y=5t6e3t            ......(1)

Write the homogeneous differential equation of the equation (1),

y''-6y'+9y=0

The auxiliary equation for the above equation,

r2-6r+9=0

Step 3: Now find the roots of auxiliary equation

Solve the auxiliary equation,

r2-6r+9=0(r-3)2=0

The roots of auxiliary equation are,

r1=3,   &   r2=3

The complimentary solution of the given equation is,

yc=c1e3t+c2te3t

Step 4: Final conclusion

To find a particular solution to the differential equation;

ay''(x)+by'(x)+cy(x)=Ctmert

Compare with the given differential equation,

y''-6y'+9y=5t6e3t

Condition satisfied,

M=6, s = 2 if r = 3 is a double root of the associated auxiliary equation.

Therefore, the particular solution of equation,

yp(x)=t2(A6t6+A5t5+A4t4+A3t3+A2t2+A1t+A0)e3typ(x)=(A6t8+A5t7+A4t6+A3t5+A2t4+A1t3+A0t2)e3t

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