जब x = 0 है तो अवकल समीकरण \(\frac{{{d^2}y}}{{d{x^2}}} - 3\frac{{dy}}{{dx}} + 2y = {e^x},\;y = 3\) और \(\frac{{dy}}{{dx}} = 3\) का समाधान क्या है

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  1. y = 2ex + e2x - xex
  2. y = ex – e2x + xex
  3. y = 2ex + e-2x – xe-x
  4. y = ex + 2e2x – x2ex

Answer (Detailed Solution Below)

Option 1 : y = 2ex + e2x - xex

Detailed Solution

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संकल्पना:

nवीं कोटि के एक रैखिक अवकल समीकरण के समाधान में दो भाग शामिल हैं। वे हैं:

  • पूरक फलन
  • विशेष समाकल

यानी y = C.F. + P.I.

गणना:

दिया हुआ:

\(\frac{{{d^2}y}}{{d{x^2}}} - 3\frac{{dy}}{{dx}} + 2y = {e^x},\;y = 3\;and\;\frac{{dy}}{{dx}} = 3\;when\;x=0\)

पूरक फलन (CF):

R.H.S = 0 डालें और मूलों की गणना करें।

\(\frac{{{d^2}y}}{{d{x^2}}} - 3\frac{{dy}}{{dx}} + 2y = 0\)

मूलों को खोजने के लिए d/dx = m डालें।

∴ m2 - 3m + 2 = 0

∴ m = 1 और 2

∴ y = C1ex + C2e2x

विशेष समाकल (PI):

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

\(\frac{1}{2D\;-\;3}xe^x\)     [∵ f(D) = 0 जब D = 1]

∴ P.I = -xex

सामान्य समाधान yy = C1ex + C2e2x - xeहै

जब x = 0, y = 3।

C 1 + C 2 = 3 ...... (1)

जब x = 0, dy/dx = 3।

\(\frac{dy}{dx}=C_1e^x\;+\;2C_2e^{2x}\;-\;xe^x\;-\;e^x\)

∴ 3 = C1 + 2C2 - 1

∴ C1 + 2C2 = 4  ........ (2)

(1) और (2) को हल करना C1 = 2 और C2 = 1 देता है।

∴ y = 2ex + e2x - xex

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