Differential Equations

[Julian]

(x^2)y'' + 2xy' - 2y = 6x^-2 + 3x, x>0

Anyone know how to solve this? for a general solution.

This is not a HW question, I'm studying for an exam today, and this is the only type of problem that I wasn't able to solve.

So steps to the solution so I can understand it would be greatly appreciated, thanks.

edit: So far I got, using the Cauchy-Euler thing, I got the answer to the homogeneous part, c1x^-2 + c2x, but for finding a particular solution.... uhhhhh >.>

[Woozie]

I'll take a shot at this when I get home. I need to review my old books first. I haven't done anything like this since I was in high school.

[Zoolander]

High school? What the fuck, the more I learn about other HS programs the angrier I become at the Florida education system.

[Woozie]

We didn't have a DiffEQ class. I just read the book because I didn't want to wait till college to learn it.

[Suiram]

My HS had a differential equations class, but I didn't take it. I also didn't take it at the university, but now I need to know it (just the basic important points, what you'd cover in your standard class, I guess). Can anyone recommend a good book to do that, that I could cover in 2-3 days and would hit all the essential ideas? This is something that I've been needing/putting-off lately, it's just a coincidence that this thread popped up, but I figured it's a good place to ask. Sorry for semi-hijacking.

[Woozie]

I used Dennis Zill's book. It's the only DiffEQ book I've ever read, so I can't say how it compares with others, but it seemed like a good book to me. It took me 7 days to read the entire book and do the problems my teacher's husband had assigned for me to do (her husband taught DiffEQ. He gave me the book and the syllabus with all the homeworks in it and told me to learn it on my own).

Of course, those were 7 days during Christmas break where I did virtually nothing but study (even missed Christmas). Depending on how much free time you have, you can probably read the entire book in a few days or a few weeks.

Edit: I can't find the actual book I used on amazon. It had a picture of a bridge on the front, I think. I see one with a bridge on the front, but it doesn't look the same as the one I have. The books I see on amazon for Zill have like 600 pages. Mine was only like 200 I think.

It might be easier to just grab a book on advanced engineering mathematics or mathematical methods for physical sciences and read their DiffEQ chapter. It will have only what you need to know (since you seem like you only want the important stuff).

[Demosthenes11]

i did DEs up to euler in HS because our calc teacher just thought it would be fun to teach us. In first year calc, we learned all of AB and BC (took it junior year). The next year, there were 11 of us that had not graduated yet that had taken his calc the previous year, so he made a new class for us and just called it calc BC officially. We did vectors, DEs, circuits, a little multivariable, and w/e else he felt like teaching us. On days we didnt feel like doing anything he would play apples to apples or poker with us. He also took us on his yacht several times. Did I mention dude owns a few exotic car dealerships?

He won teacher of the year a while back. Only reason I miss HS

[Eliseos]

The more math classes someone takes, the higher their salary is. Except you, Woozie, sorry.

[Woozie]

The more math classes someone takes, the higher their salary is. Except you, Woozie, sorry.

You know, just this morning I was ranting to this applied math guy about how it's not fair that they have more jobs and make more money than us. Then I started to complain about engineers, and he was like "oh yeah that's my second major". Him and I are now mortal enemies.

And if I ever become president (or when my plans for world domination succeed), I'll make it so that applied mathematicians/scientist have to pay royalties to theoretical people.

Edit: Demos11, where the heck did you go to school? That's the kind of stuff Zoolander (and everyone else) should be raging about. We didn't even have calc based physics at my HS let alone someone who was teaching multivariable calc, diffeq, and circuts, etc. And how does a HS teacher have exotic cars and a yatch?

Edit 2: I read that wrong, he owns the dealership, hence why he can afford a yatch. But then why is he teaching high school?

[Demosthenes11]

who cares if you can do math, it's how you apply it!
(I'm applied math major lol)

[Woozie]

(I'm applied math major lol)

Demos11 and I are also mortal enemies now too.

[Jefe]

You know, just this morning I was ranting to this applied math guy about how it's not fair that they have more jobs and make more money than us. Then I started to complain about engineers, and he was like "oh yeah that's my second major". Him and I are now mortal enemies.

I was going to double Mathematics but my EE/CE adviser was telling me most engineers (or vice versa) go that route. I chose business.

[Demosthenes11]

Demos11 and I are also mortal enemies now too.

it's ok, you will drive yourself crazy with knowledge and I will drive myself crazy in a cubicle

different means to the same end

[Woozie]

But you'll get paid more to drive yourself crazy.

[Julian]

Tons of replies and no answer

not that it matters, already had my exam, and I'm sure I failed it.

I was so prepared and 100% ready, and all the stuff he asked where little tiny things that i didn't exactly get to look over, or were slightly different, and i missed one tiny part, probably gonna lose a lot of points unless he's nice with partial credit :/ i dunno, at least i get one exam drop so it's not that bad, just gotta... study more i guess? even tho I felt like I studied A LOT this time :/

[Purrrfect]

You might get lucky and do fine. I know when I took DEQ I never really felt I had a 'good' grasp on it, but I'm pretty sure I made a B or A in it. Now (prolly 5 years later) I can not remember a single thing from it, and all I can come up with for your OP w/o using google to relearn is 'wtf'. ;; The problem with going part time, you never remember shit cuz its too spread out and not reinforced. I can't remember anything past regular calc2 I think, and a few key spots there are empty too...

[Kaylia]

First thought: Yay, a maths question
Second thought: fuck, a differential equation


If it's not a sin cos answer, count me out lol. Homogeneous are fine, but everything else, I don't think I've solved any since my differential class, or at least, none without mathematica.

[Eliseos]

First thought: Yay, a maths question
Second thought: fuck, a differential equation


If it's not a sin cos answer, count me out lol. Homogeneous are fine, but everything else, I don't think I've solved any since my differential class, or at least, none without mathematica.

This. The only differential equations I can solve now are when dx/x is involved, or ax'' + bx' + c = 0.

[Xrave]

who cares if you can do math, it's how you apply it!
(I'm applied math major lol)

Guy on Street #2: It's 3:00. Where the hell is Louie?
Guy on Street #1: Well, you tell me. Louie left his house at 2:15 and had to travel a distance 6.2 miles traveling at a rate of five miles a hour. When will Louie get here?
Guy On Street #2: Depends if he stops to see his ho.
Guy on Street #1: That's what we call a "variable".

[Pirian]

If it's not a sin cos answer, count me out lol. H

Think you could be my study buddy for electromagnetism? lol This stuff is kicking my butt, ugh I hate math so much, but at the same time this stuff is so interesting lol