
Differential Equations Ordinary and Partial Differential Equations Math Forum 
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October 28th, 2012, 08:42 PM  #1 
Senior Member Joined: Aug 2012 From: South Carolina Posts: 866 Thanks: 0  My First Differential Equation
Book says solve the following Differential Equation dy/dx = 8x^(3)  9X^(2) + 4 I will try but need the forum's help dy = (8x^(3) 9x^(2) +4) dx y = 8x^(4)/(4)  9x^(3)/(3) +4x + C Is this done? 
October 28th, 2012, 08:45 PM  #2 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs  Re: My First Differential Equation
Almost, you just need to reduce your fractions. Good work! 
October 28th, 2012, 08:50 PM  #3 
Senior Member Joined: Aug 2012 From: South Carolina Posts: 866 Thanks: 0  Re: My First Differential Equation
Mark, I can do that lol I have about 15 to work through over the next day and a half Will you show me one so I can use it as a reference problem. Here is a rather simple one but I want to take note and follow step by step from start to finish how you guys do here goes... dy/dx =( x^(2) + 2x 3 ) / (x^(4)) 
October 28th, 2012, 09:07 PM  #4 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs  Re: My First Differential Equation
We are given: Integrate with respect to x: 
October 29th, 2012, 01:14 PM  #5 
Senior Member Joined: Aug 2012 From: South Carolina Posts: 866 Thanks: 0  Re: My First Differential Equation
Mark, This is a perfect for reference material. The very last step. Can you explain the Algebra to me on that one? Why did you pull the C back? Thanks like always Mark. I really appreciate being able to reference this here. 
October 29th, 2012, 03:03 PM  #6 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs  Re: My First Differential Equation
I dislike leading negatives, so I simply put the constant in front.

October 29th, 2012, 07:38 PM  #7 
Global Moderator Joined: Dec 2006 Posts: 21,026 Thanks: 2257 
How come the book doesn't provide worked examples for reference?

October 29th, 2012, 07:51 PM  #8 
Senior Member Joined: Aug 2012 From: South Carolina Posts: 866 Thanks: 0  Re: My First Differential Equation
Well it does skip. I am taking 2 calc classes this semester. calc1 and biz calc. The biz calc class book cost near 400. it is very nice and is used for 2 and 3 as well. The instructor does make constant comments about how the book does tell this and the book doesn't tell this. I told him tonight I was going to have to put a lot of weight on him 
October 30th, 2012, 10:44 AM  #9 
Global Moderator Joined: Dec 2006 Posts: 21,026 Thanks: 2257 
The basics of calculus are reasonably easy, but you need to understand elementary algebra as well.

October 30th, 2012, 04:40 PM  #10 
Senior Member Joined: Aug 2012 From: South Carolina Posts: 866 Thanks: 0  Re: My First Differential Equation
I was thining about this last night in class skippy when instructor said that we were now moving into the first Fundamental Theroem of Calculus Almost 90% Algebra. If this is true, I believe many if not all Calculus students refine and grow and develop their Algebra in the Trig and Calculus 1,2&3 (if they get that far). I'll have you and Mark and anybody else on this forum know a few things: Every student in my class struggles with the Algebra in both of my Calculus classes( Intro Calc and Biz Calc w/ Analytical Geometry). There Algebra is no better then mine and most are obviously out of practice. So what do you have to say about that Skip? #2) I will have you and the others know this about me. I will take only so much mouth and verbal abuse(including subliminal text) I am taking 2 calc classes this Semester to get a better grip and plan to re take Trig next Semester as I found very challenging and like I already told Mark here on this forum... had a foriegn teacher who I personally felt was a horrible teacher/leader/instructor. I will however only asign so much blame on him and not if but when I retake will give 300% more this time around and make an A in Trig for personal triumpth. #3) As an aspiring math major, I plan to go far past the math that community colleges teach and will pound this forum all the way through. Do you hear me Skip? I heard you are quite the Genius yourself and very CLEVER and I mean no disrespect to you and/or Mark(whom I like a lot) but I will have you and the others know that when the going gets tough... I get 10x tougher. I was not top Mortgage Loan Officer for 7+ years at every and all co's I worked for nor the fund raising salesman who broke all the records the company had set ... (because I am weak!) Students need to be told firmly but assisted (I feel Mark is excellent in this area) ... and given onstructivle criticism not destrucively. Let me re emphacize the fact that I will pound pound pound this forum as I grow as a mathy and can always re created if I have too. Skip you might be thinking (bring it kid!) but I promise you that I will if I am not mentored but abused. Thanks Skip! 

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