What is the general solution of the differential equation dy/dx−2xy=x?

Lindsey Ibarra

Lindsey Ibarra

Answered question

2022-09-27

What is the general solution of the differential equation d y d x - 2 x y = x ?

Answer & Explanation

brodireo1

brodireo1

Beginner2022-09-28Added 12 answers

d y d x - 2 x y = x

Which we can write as:

d y d x = 2 x y + x
d y d x = ( 2 y + 1 ) x
1 2 y + 1 d y d x = x

Which is a first order separable differential equation, so we can "separate the variables" to get:

  1 2 y + 1   d y =   x   d x

Integrating we get, the General Solution:

1 2 ln | 2 y + 1 | = 1 2 x 2 + C

Applying the initial condition y(1)=1 we find:

1 2 ln 3 = 1 2 + C C = 1 2 ln 3 - 1 2

So we can write an implicit particular solution as:

1 2 ln | 2 y + 1 | = 1 2 x 2 + 1 2 ln 3 - 1 2

We typically require an explicit solution, so we can rearrange as follows:

ln | 2 y + 1 | = x 2 + ln 3 - 1
| 2 y + 1 | = e x 2 + ln 3 - 1

Noting that the exponential function is positive over its entire domain, (as e x > 0 x ):

2 y + 1 = e x 2 - 1 e ln 3

2 y = 3 e x 2 - 1 - 1

y = 3 2 e x 2 - 1 - 1 2

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