# P4 - 2 differential eqn toufiesWatch

Announcements
#1
anyone pls. help me solve this

dy/dx - (1+3x^-1)y = x + 2, y(1) = e -1

The answer to this is y = -x + x3ex.

and the next qn. is

dy/dx + y + x/y = 0

would be grateful for all ur help
0
13 years ago
#2
(Original post by studentruzaika)
anyone pls. help me solve this

dy/dx - (1+3x^-1)y = x + 2, y(1) = e -1

The answer to this is y = -x + x3ex.

and the next qn. is

dy/dx + y + x/y = 0

would be grateful for all ur help
I'm willing to help, but I can't understand the initial conditions for the first one.
y(1) = e -1
0
13 years ago
#3
Is there anything els you can write in terms of a fuller question? Its a bit vague you've given us the answer but im not sure entirely wat you want 2 be found and is y=e-1 a subsititution?
0
#4
(Original post by Fade Into Black)
Is there anything els you can write in terms of a fuller question? Its a bit vague you've given us the answer but im not sure entirely wat you want 2 be found and is y=e-1 a subsititution?
its the value of y at 1 hence y(1)
0
13 years ago
#5
I'm sorry but the question is very badly typed.
Is it e^-1 or e - 1?
0
13 years ago
#6
I get the integrating factor to be 1/(e^x x^3) - which sets up a couple of horrible integrals.
0
13 years ago
#7
(Original post by studentruzaika)
anyone pls. help me solve this

dy/dx - (1+3x^-1)y = x + 2, y(1) = e -1

The answer to this is y = -x + x3ex.
INTEGRATING FACTOR is 1/(x^3.e^x)

x^-3.e^-x.dy/dx + (-x^-3.e^-x -3x^-4.e^-x)y = (x+2)/(x^3.e^x)
=> d(x^-3.e^-x.y)/dx = (x+2)/(x^3.e^x)
=> x^-3.e^-x.y = (x+2)/(x^3.e^x) = x^-2.e^-x + 2x^-3.e^-x

That's as far as I get. Now if someone could intepret what the OP has typed that would be very useful.
0
#8
i believe this is the answer. i have attached it..
u have to use partial fractions on the integral of e^-x.x^-3
0
X

new posts
Back
to top
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

### University open days

• Norwich University of the Arts
Thu, 23 Jan '20
• SOAS University of London
Development Studies, Interdisciplinary Studies, Anthropology and Sociology, Languages, Cultures and Linguistics, Arts, Economics, Law, History, Religions and Philosophies, Politics and International Studies, Finance and Management, East Asian Languages & Cultures Postgraduate
Sat, 25 Jan '20
• University of Huddersfield
Sat, 25 Jan '20

### Poll

Join the discussion

0 (91)
13.07%
1 (89)
12.79%
2 (89)
12.79%
18.97%
22.56%
19.83%