# differential equation of a function determined by own increment at x-A

#### nasi112

##### Full Member
You had a beautiful differential equation in the first part.

Do you mean this?

$$\displaystyle \frac{dy}{dx} = \frac{(H - By)}{A}$$

In the second part. I don't understand your differential equation.

Do you mean this?

$$\displaystyle \frac{dy}{dx} = \frac{H - By + B \ dy}{A}$$

I am sorry, but this is not a correct differential equation!

#### fogoetha

##### New member
You had a beautiful differential equation in the first part.

Do you mean this?

$$\displaystyle \frac{dy}{dx} = \frac{(H - By)}{A}$$

In the second part. I don't understand your differential equation.

Do you mean this?

$$\displaystyle \frac{dy}{dx} = \frac{H - By + B \ dy}{A}$$

I am sorry, but this is not a correct differential equation!
Dear @nasi112
Yes, I indicated that the formulation was inadequate.
but you also mean that the equation proposed by you is not even a valid formulation? This can be easily rewritten to contain only one 'dy', so I don't see the problem.
The real problem is that the additional dy should not refer to 'x' but to 'x-A'. I don't know how to incorporate this.

#### Subhotosh Khan

##### Super Moderator
Staff member
Hi everyone,
I posted below question on mathforums.com half a year ago, but never got any reponse. So I hope someone can help me out here:

View attachment 27722
kind regards
Frederik
What is the context of the problem? In other words, how did this problem arise - how was it formulated?

#### nasi112

##### Full Member
Dear @nasi112
Yes, I indicated that the formulation was inadequate.
but you also mean that the equation proposed by you is not even a valid formulation? This can be easily rewritten to contain only one 'dy', so I don't see the problem.
The real problem is that the additional dy should not refer to 'x' but to 'x-A'. I don't know how to incorporate this.
Show me how will you do it.

#### Subhotosh Khan

##### Super Moderator
Staff member
Dear @nasi112
Yes, I indicated that the formulation was inadequate.
but you also mean that the equation proposed by you is not even a valid formulation? This can be easily rewritten to contain only one 'dy', so I don't see the problem.
The real problem is that the additional dy should not refer to 'x' but to 'x-A'. I don't know how to incorporate this.
What is the context of the problem? In other words, how did this problem arise - how was it formulated?
Please answer the question/s posed above.

• nasi112