Question Details

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

A

2yey = ex + e

B

y2ey = ex

C

yey = ex

D

(i + y)ey = 2ex

Correct Answer :

yey = ex

Solution :

The correct option is yey = ex.

To find the solution to the given differential equation, we start with the equation:
( 1 + y ) d y d x = y

We can solve this differential equation by using the method of separation of variables. Let's rearrange the terms to group all y-terms on one side and x-terms on the other side:
1 + y y d y = d x

Simplifying the fraction on the left-hand side gives:
( 1 y + 1 ) d y = d x

Now, we integrate both sides of the equation:
( 1 y + 1 ) d y = d x

Integrating term by term, we get:
ln | y | + y = x + C
where C is the constant of integration.

We are given the initial condition y(1) = 1, which means y = 1 when x = 1. Let's substitute these values into our integrated equation to solve for C:
ln ( 1 ) + 1 = 1 + C

Since ln(1) = 0, the equation simplifies to:
0 + 1 = 1 + C C = 0

Substituting C = 0 back into the general solution, we obtain:
ln ( y ) + y = x

To convert this equation into the form of the options, we exponentiate both sides (raise e to the power of both sides):
e ln ( y ) + y = e x

Using the laws of exponents, we can rewrite the left-hand side:
e ln ( y ) e y = e x

Since eln(y) = y, we get:
y e y = e x

This matches the correct option.

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