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Differential Equations

Question
CBSEENMA12033089

The general solution of the differential equation dy over dx space equals space straight e to the power of straight x plus straight y end exponent is
  • ex + e– y = C
  • e+ ey = C
  • e– x + ey = C
  • e– x + e–y = C

Solution

A.

ex + e– y = C The given differential equation is
                  dy over dx space equals space straight e to the power of straight x plus straight y end exponent space space space space space or space space dy over dx space equals space straight e to the power of straight x. space straight e to the power of straight y
Separating the variables, we get,
                       1 over straight e to the power of straight y dy space equals space straight e to the power of straight x space dx
Integrating,     integral straight e to the power of negative straight y end exponent dy space equals space integral straight e to the power of straight x space dx
therefore space space space space fraction numerator straight e to the power of negative straight y end exponent over denominator negative 1 end fraction space equals space straight e to the power of straight x plus straight c apostrophe
therefore space space space space space space minus straight e to the power of negative straight y end exponent space equals space straight e to the power of straight x plus straight c apostrophe space space or space space straight e to the power of straight x plus straight e to the power of negative straight y end exponent space equals space minus straight c apostrophe
therefore space space space space straight e to the power of straight x plus straight e to the power of negative straight y end exponent space equals space straight C comma space which space is space required space solution. space
therefore space space left parenthesis straight A right parenthesis space is space correct space answer.

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