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Unformatted text preview: Section 4.2 (then 4.1) 2nd order DFQ with constant coefficients Feb 24, 2009 Characteristic Method Todays Session Section 4.2, contd A Summary of This Session: (0) Yet another example of variation of parameters (1) Solving constant coefficient homogeneous DFQs (1st order, second order, 3rd order, etc); (2) Characteristic Equation with real or repeated roots; (3) Concepts of linearity and independence; (4) nonhomogeneous DFQ with particular and general solutions. Characteristic Method Example (a) Verify that y 1 = e x is a solution of dy dx = e 2 x + (1 + 2 e x ) y + y 2 (b) Let y = y 1 + 1 v be a solution of the DFQ. Find a differential equation satisfied by v . (c) Solve the differential equation in part (b) and write down the solution for the original DFQ. Answers: (b) v + v = 1; (c) v = 1 + Ce x and y = e x + 1 Ce x 1 . Characteristic Method Back to Constant Coefficients Second Order DFQs Example 1: (a) Solve 6 y  y  2 y = 0. (b) Solve the IVP: 6 y  y  2 y = 0 subject to y (0) = 4 and y (0) = 5. (c) Find the general solution of the nonhomogeneous problem 6 y  y  2 y = x 2 x + 3 ....
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 Spring '09
 Lotfi
 Differential Equations, Equations

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