1.

Give the complete solution of this general linear homogeneous function.y'''- y'' = e3x + 3e4x

Answer»

Given differential equation is y'''-y''=e3x+3 e4x

It's auxiliary equation is 

m3-m2 = 0

= m2(m-1) = 0

= m = 0, 0 & 1.

∴ CF = (C1 + C2x)e0x + C3ex

= C1 + C2x + C3ex

P.I.  = \(\frac {1}{D^3-D^2} (e^{3x} + 3e^{4x)}\)

\(\frac {1}{D^2(D-1)}e^{3x} + \frac {3}{D^2(D-1)}e^{4x}\)

\(\frac {e^{3x}}{3^2(3-1)} + \frac {3e^{4x}}{4^2(4-1)}\)

\(\frac {e^{3x}}{18} + \frac {3e^{4x}}{48}\)

\(\frac {e^{3x}}{18} + \frac {e^{4x}}{16}\)

∴ Complete solution of given differential equation is 

y = CF + P.I.

= C1 + C2x + C3ex\(\frac {e^{3x}}{18} + \frac {e^{4x}}{16}\)



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