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how to solve 4th order differential equations

Posted 9 years ago

Hi could you please help me out to solve a 4th order differential equation in mathematica with initial values:

enter image description here

Regards

POSTED BY: Muhammad Afzal
3 Replies

A first step might be to solve the homogeneous equation:

In[13]:= DSolve[D[y[x], {x, 4}] - x y[x] == 0, y[x], x]

Out[13]= {{y[x] -> 
   C[1] HypergeometricPFQ[{}, {2/5, 3/5, 4/5}, x^5/625] + (1/(5^(
    4/5)))(-1)^(1/5)
      x C[2] HypergeometricPFQ[{}, {3/5, 4/5, 6/5}, x^5/625] + (1/(
    5 5^(3/5)))(-1)^(2/5)
      x^2 C[3] HypergeometricPFQ[{}, {4/5, 6/5, 7/5}, x^5/625] + (1/(
    25 5^(2/5)))(-1)^(3/5)
      x^3 C[4] HypergeometricPFQ[{}, {6/5, 7/5, 8/5}, x^5/625]}}

then try one of the standard techniques for the corresponding inhomogeneous equation.

For a numerical solution

In[19]:= NDSolve[{D[y[x], {x, 4}] - 
    x y[x] == -(11 + 9 x + x^2 - x^3) E^x, y[-1] == 0, y[1] == 0, 
  y'[-1] == 2/E, y'[1] == -2/E}, y[x], x]

Out[19]= {{y[x] -> \!\(\*
TagBox[
RowBox[{"InterpolatingFunction", "[", 
RowBox[{
RowBox[{"{", 
RowBox[{"{", 
RowBox[{
RowBox[{"-", "1.`"}], ",", "1.`"}], "}"}], "}"}], ",", "\<\"<>\"\>"}],
         "]"}],
False,
Editable->False]\)[x]}}
POSTED BY: S M Blinder
Posted 9 years ago

Thank You S M Blinder its a gr8 help Regards

POSTED BY: Muhammad Afzal
Posted 9 years ago

Look at the examples in the documentation for NDSolve

NDSolve

try to carefully model your input after the examples, and use E for Euler's constant, or use one of the palettes to enter a desktop-published version of E. Watch carefully that it is always y''''[t] and y[t], not the more usual math notation of y''''' and y.

See if that provides you with enough insight to complete this.

POSTED BY: Bill Simpson
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