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Engineering Mathematics Miscellaneous

Engineering Mathematics

Direction: The complete solution of the ordinary differential equation

d2y
+ p
dy
+ qy = 0 is
dx2dx

y = c1e-x + c2e-3x

  1. Which of the following is a solution of the differential equation
    d2y
    + p
    dy
    + (q + 1)y = 0 ?
    dx2dx

    1. e-3x
    2. xe-x
    3. xe-2x
    4. x2e-2x
Correct Option: C

d2y
+ p
dy
+ (q + 1)y = 0
dx2dx

∴ D2 + pD + (q + 1) = 0
⇒ D2 + 4D + 4 = 0
Since, p = 4, q = 3, therefore
⇒ D =
-4 ± √16 - 16
= -2
2

Hence, it's solution is, = xeDx = xe–2x



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