Question

Consider the following differential equation

( 1 + y ) d y d x = y

The solution of the equation that satisfies the condition y(1) = 1 is

Options :

  1. 2yey = ex + e

  2. y2ey = ex

  3. yey = ex

  4. (i + y)ey = 2ex

Show Answer

Answer :

yey = ex

Solution :

(1 + y) d y d x = y

( 1 + y ) y dy = dx

1 y dy + 1dy = dx

Integrating both side,

1 y d y + 1 d y = d x + C

lny + y = x + C

at x = 1, y = 1

ln1 + 1 = 1 + C

C = 0

So, lny = (x - y)

y =  e ( x     y ) e x e y

yey = ex

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