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After calculus first pure math course, having a hard time. 
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#1
Feb1314, 11:41 PM

P: 87

I just started number theory, and I feel completely lost. I never did proofs in calc. I am used to watching the professor do examples, then with solutions manual at home see how the problems are done and use the manual if I get stuck. This book on NT has no homework problems or solutions. I just don't really know where to start on problems? The professor just basically does proofs every class, and they are very hard to follow. I get lost early in the proof, then don't know what to do. I have done very well through calc, not sure what to do. Suggestions?



#2
Feb1414, 08:03 AM

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Hi chimath35!
Have you tried googling 'number theory exercises'? There must be others in your class in the same boat. Team up with someone and attack some practice exercises together. Can you get hold of past years' asignments or exam papers in your subject? Good luck! 


#3
Feb1414, 09:33 AM

P: 87

Okay, you mean like ask the prof. for past exams or try to find other students who took the course?



#4
Feb1414, 10:02 AM

P: 160

After calculus first pure math course, having a hard time.
You have a difficult task before you because the skills needed to succeed in this class are almost entirely different from those needed to succeed in a calculus class.
If your professor does not give you homework, you must locate problems in some other way (ask your professor, or look in the library for some of the books listed here), but be aware that "problems" no longer refers to routine exercises in carrying out algorithms, as it did in calculus. You should expect each problem to be a difficult endeavor that requires creativity and cleverness. You will not know how to do the problems at first, and it will take you a very, very long time to solve them (especially while you are just starting), so do not be discouraged. And above all, do not ever look solutions to the problems before you have solved them! If you don't know how to do the problem, you can either keep thinking about it until you figure it out, or give up, but it is the act of thinking about it that causes you to learn, so don't just look at the solution. If you are not sure if your solution to the problem is correct, ask the professor. 


#5
Feb1514, 06:32 PM

P: 87

Ya, I just can't seem to figure these out. Even with solutions, it is like the more I look at it the more confused I am. I feel honestly just terrible about this. I don't know what to do. I can't keep getting this mad, not good. Like I have five problems and can solve none. Have gotten straight A's almost and I feel like I would get a 10 percent on an exam for this.



#6
Feb1514, 06:34 PM

P: 87

I see formulas that are equal to each other try using them and end up solving none. It is so abstract, and just so many letters and it is like making my head spin. I honestly don't know what to do.



#7
Feb1514, 07:33 PM

P: 255

Maybe you can post one of the questions in the forum, and see if the mentors can guide you step by step with it?



#8
Feb1514, 07:50 PM

P: 361

Does your college have an "introduction to proofs" course, or something similar? If so, you might wish to take that course. Proving theorems is very different from calculations found in calculus. You might find this web page useful. The author describes five proof techniques that are used in basic number theory.



#9
Feb1514, 09:14 PM

Mentor
P: 21,292

There are a couple of books that might help you.
"How to Read and Do Proofs"  Daniel Solow "The Nuts and Bolts of Proofs"  Antonella Cupillari If you do a search on Amazon or other bookseller you should find them. Both are paperbacks. As I recall, one was a bit pricy, but the other wasn't that expensive. Either one would be helpful to you, I believe. 


#10
Feb1614, 02:28 AM

P: 87

These might be simple to you guys but these problems are MUCH harder to me than some hard calculus word problems.
here is my hw: 1) If a l b and that a & b are positive, then a < b unless a = b. 2) If a l b, then a l nb for any integer n. If a l nb for some integer n, can you conclude that a l b? 3) If a l (b + c) and a l (b + d), then a l (d  c) and a l (c  d). Can you conclude that a l b? 4) If a l b, then a l b^{n} for any positive integer n. If a l b^{n} for some positive integer n, can you conclude that a l b? 5) Can there be an even prime greater than 2? Write 365 as a product of primes 


#11
Feb1614, 02:43 AM

P: 255




#12
Feb1614, 02:52 AM

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If you are completely stuck with a problem, start by playing around with some numbers to see what the problem means, and (with luck) get a clue how to do the proof.
For example the first one: "If a l b and that a & b are positive" Suppose b = 6 (I'm just picking a number that has a few different divisors, there's nothing special about 6) what values can a have? Why can't a be bigger than 6? Then, as Seydlitz said, you have to use the definition of what "a  b" means..... 


#13
Feb1614, 12:33 PM

P: 87

Ya, see I have the notes and formulas we are supposed to use, I play with them and end up not being able to solve them. I don't like this math class at all. I was pumped about math after multi v calc. It is like I don't want to spend hours burning out my brain and taking a LOT of time just trying to figure out a few to me boring problems. This kind of math is so boring and time consuming to me not to mention I do have other classes that I need to have time for and don't like burning my brain out with such "max" effort on these problems. I feel like I have to think so ridiculously weird and hard on these.



#14
Feb1614, 12:38 PM

P: 87

These problems are like a game to me. I am not a fan of trying and failing, trying and failing to try to solve one in my opinion boring problem. From gradients to this? Are there other types of mathematics that I can study that are not so boring, not so time consuming, and not such a hard game? Like I said I like multi v calc A LOT. I want to do math like that I guess.



#15
Feb1614, 12:41 PM

P: 87

Also, I guess I get so bummed from not being able to solve these as well that I honestly get upset and think well I tried and I don't get it; I do have a life and other things to do so I stop. There is really no where for me to go for help at my uni. with this level math either. The help is limited on this.



#16
Feb1614, 01:17 PM

P: 1,622




#17
Feb1614, 06:32 PM

Mentor
P: 21,292

Many math courses beyond calculus involve problems where you prove a statement rather than, say, find a derivative or evaluate an integral. For example, many students struggle just as hard with linear algebra as you are with number theory. Either of the books I suggested back in post #9 will give you lots of examples of the various types of proofs (e.g., direct proofs, proof by contradiction, contrapositive, and so on).



#18
Feb1714, 07:48 PM

P: 19

Proof by contradiction sounds like a great way to attack some of the problems you listed. Unless you're a constructivist. In number theory, induction is a very important tool too. For the first one, why can't a divide b if a>b?



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