Is this general solution correct?

In this case, when you substitute ##y = Ce^{-at} + \frac b a## in the original equation ##\frac{\mathrm{d}y}{\mathrm{d}t} = -ay + b##, you get ##\frac{\mathrm{d}}{\mathrm{d}t}(Ce^{-at} + \frac b a) = -a(Ce^{-at} + \frac b a) + b## which simplifies to ##-aCe^{-at} + b + aCe^{-at} + b = b##, which is a true statement. So, your solution satisfies the differential equation. In summary, the general solution of the differential equation dy/dt = -ay +
  • #1
xavier777
2
0
Question : General solution of dy/dt = -ay + b
My solution :

dy/dt = -a(y-b/a)
(dy/dt)/(y-(b/a)) = -a

Integrating both sides :
ln | y-(b/a) | = -at + C
e(-at+C) = y-(b/a)
Ce(-at) = y-(b/a)
 
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  • #2
xavier777 said:
Question : General solution of dy/dt = -ay + b
My solution :

dy/dt = -a(y-b/a)
(dy/dt)/(y-(b/a)) = -a

Integrating both sides :
ln | y-(b/a) | = -at + C
e(-at+C) = y-(b/a)
Ce(-at) = y-(b/a)
Or ##y = Ce^{-at} + \frac b a##
Did you check to see if your solution satisfies the diff. equation?
 
  • #3
How do I do that? Differentiate it to get back to the original diff eq ? If yes, then what about the assumption eCe-at = Ce-at ?
 
  • #4
xavier777 said:
How do I do that? Differentiate it to get back to the original diff eq ? If yes, then what about the assumption eCe-at = Ce-at ?
Substitute your solution in the original differential equation and you should get a true statement.
 

What is a general solution?

A general solution is a mathematical expression that satisfies a given equation or set of equations. It includes all the possible solutions to the equation, rather than a specific one.

How do you know if a general solution is correct?

A general solution can be checked by plugging it into the original equation. If it satisfies the equation, then it is considered a correct solution.

Can a general solution be unique?

Yes, a general solution can be unique if the equation only has one solution or if the general solution is expressed in terms of a constant.

Why is it important to find a general solution?

Finding a general solution allows for a better understanding of the behavior of a system or equation. It also provides a way to find specific solutions for different values of variables.

Are there different methods for finding a general solution?

Yes, there are different methods for finding a general solution depending on the type of equation. Some common methods include separation of variables, substitution, and using specific formulas for certain types of equations.

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