A differential equation question

  • Thread starter mech-eng
  • Start date
  • #1
760
11

Main Question or Discussion Point

There is differential equation with initial condition perplexing me.

y'+ y = 1, y = ce^-x + 1 , y = 2.5 when x = 0

First I take derivative of y which is -ce^-x then I sum it up with y which is -ce^-x+ce^-x + 1 equals 1 which is in harmony with y' + y = 1 but it
seems that this is independent from integral constant c and so there are infinite number of c but in the answer c is -1.5.

Have a nice day.
 

Answers and Replies

  • #2
140
14
?
y=1+c*e^(-x); at x= 0, y = 1+c*e° = 1+c=2.5, .....so, c = 1.5
 
Last edited:
  • Like
Likes 1 person
  • #3
760
11
?
y=1+c*e^(-x); at x= 0, y = 1+c*e° = 1+c=2.5, .....so, c = 1.5
Thank you.
 
  • #4
HallsofIvy
Science Advisor
Homework Helper
41,833
955
You were told, when they said "y= ce^{-x}+ 1" that this would satisfy the differential equation for all values of c. That is what that means. The problem was to find c such that y(0)= 2.5.
 
  • Like
Likes 1 person

Related Threads on A differential equation question

  • Last Post
Replies
5
Views
2K
Replies
19
Views
2K
Replies
17
Views
7K
Replies
13
Views
2K
Replies
4
Views
3K
Replies
4
Views
2K
Replies
1
Views
1K
Replies
8
Views
880
Replies
2
Views
2K
Replies
3
Views
2K
Top