Life The MangaHelpers Confessional Thread - Part 2

[Naomi]

How so?

Basically, spanning vector sets are like constructing a new random coordinate system. Forget about x,y,z; you now take v1, v2...vN.

Well the concepts aren't that out there, but that doesn't mean I know how to approach the problems. Something like:

Determine the span of {v1,v2} for the given vectors in R3 and describe it geometrically if v1 = (1,-1,2) and v2 = (2,-1,3).

The solutions on chegg go from A directly to Z. There are virtually no intermediate steps. And my teacher just flies through the material. He doesn't explain examples fully either. :/ I'm just hoping the exam isn't too involved.

 

[earthforge]

Well the concepts aren't that out there, but that doesn't mean I know how to approach the problems. Something like:

Determine the span of {v1,v2} for the given vectors in R3 and describe it geometrically if v1 = (1,-1,2) and v2 = (2,-1,3).

Basically you have two points defined in R3. What is the set of all possible linear combinations of these two points? We can write them as av1+bv2. Thus all elements in the span have the form:

(a+2b, -a-b, 2a+3b)

EDIT: Okay, so you set your new linear combination vector (a+2b, -a-b, 2a+3b) equal to (x, y, z).

You can now observe that y + z = (2a + 3b) + (-a - b) = a + 2b = x.

This is the form of your solution. Each y and z value determines x.

 

[Adorien]

The Confessional thread has turned into a Maths field...

 

[jorped]

Well the concepts aren't that out there, but that doesn't mean I know how to approach the problems. Something like:

Determine the span of {v1,v2} for the given vectors in R3 and describe it geometrically if v1 = (1,-1,2) and v2 = (2,-1,3).

The solutions on chegg go from A directly to Z. There are virtually no intermediate steps. And my teacher just flies through the material. He doesn't explain examples fully either. :/ I'm just hoping the exam isn't too involved.

I remember doing this kinda stuff on Algebra on my first year on university. Honestly it doesn't strike me as hard. You just need to check some resolved exercises, and soon you will understand it. Once you start understanding it, you will start doing that super easily.

 

[Naomi]

Basically you have two points defined in R3. What is the set of all possible linear combinations of these two points? We can write them as av1+bv2. Thus all elements in the span have the form:

(a+2b, -a-b, 2a+3b)

EDIT: Okay, so you set your new linear combination vector (a+2b, -a-b, 2a+3b) equal to (x, y, z).

You can now observe that y + z = (2a + 3b) + (-a - b) = a + 2b = x.

This is the form of your solution. Each y and z value determines x.

Ohhh kay. So basically v1 and v2 span R3 in the form of y + z = (2a + 3b) + (-a - b) which is the same as a + 2b = x? Basically, I didn't understand that I just needed to generalize the two vectors over the entire span of the third dimension by picking arbitrary variables (you chose a and b in this case). That seems to make sense now.

Geometrically speaking, this would be a plane in R3, right?

I remember doing this kinda stuff on Algebra on my first year on university. Honestly it doesn't strike me as hard. You just need to check some resolved exercises, and soon you will understand it. Once you start understanding it, you will start doing that super easily.

Saying things like "this shit is easy. I did it in my first year" does not encourage or help me, you ass hole. Unless you're going to actually say something USEFUL like earthforge, then just keep your mouth shut. If the book would have showed examples similar to this or my teacher would have gone over it, I wouldn't be having this problem.

 

[Hardy]

I had to do that in first year (last year)...

Now I have to do it again

 

[Naomi]

It's like calculus 2... I survived it, but somehow I know it's going to come back to haunt me....

 

[jorped]

I guess i was kinda of a jerk. Sorry

I remember i found that easy, but i needed some practice, not like it was easy for me since the first time i saw it. Anyway, it's been more than 2 years now, so i don't honestly remember much any more, plus being in English doesn't help either.

Anyway, it kinda sucks that your teacher doesn't explain much, cuz one of the reasons why i ended this class with such a good mark was because my teacher was really good, and showed us examples of pretty much everything. But it can be indeed "hard" if you don't have anything to guide on.
Anyway, i can't really help much. And i do struggle with situations like this from time to time, where the problems isn't actually the subject, but the lack of help the teachers give us in order to fully understand and be prepared for the exam.

Sorry if i was kinda stupid. Anyway i would recommend you to try to study with some friends, or ask someone of them that is comfortable with that particularly part to explain to you. Anyway good luck for your exams, i will also need some luck for mine XD

 

[M3J]

STOP THIS MATH TALK PLZ

 

[xi0]

I hate math...it's not that I suck at it, I just dun liek et.

 

[Adorien]

I hate math...it's not that I suck at it, I just dun liek et.

But you still suck at it, right?

 

[xi0]

But you still suck at it, right?

Do you suck at reading?

Spoiler

probably

 

[Adorien]

Nah, it's just my bad English skills. xD

Spoiler

Gary: Oh, look at me, I'm a math wiz, but I hate math. <.>

 

[xi0]

Nah, it's just my bad English skills. xD

Spoiler

Gary: Oh, look at me, I'm a math wiz, but I hate math. <.>

Lol, no...that's not what I was going for. Not sucking =/= genius

 

[Adorien]

xD I know. But to me, not sucking at something means you're doing pretty well at it. But I guess you were going for average.

I hate math too. And I suck. xD I've had my moments, but I suck in general. Well I suck at everything, so.

 

[xi0]

I suck at everything too

 

[Adorien]

I suck at everything too

You just said you don't suck at math! xD

Also, I confess I am still jobless. I also confess I hate the way our mobile operators work. I got fooled in the beginning of the month to pay more than I needed to. And I may have to pay twice as much as I should have by the end of the month. But I can't do anything, because I signed the contract. And that's how contracts work. The same mistake got me in the current position, not studying what I wanted to. I just make the same mistakes over and over again. ._.

 

[earthforge]

Geometrically speaking, this would be a plane in R3, right?

Yup (I had to consult Master Google to figure that out though. ;^^)

Saying things like "this shit is easy. I did it in my first year" does not encourage or help me

I've taken linear algebra a total of four times now: at community college, at UC (because they made me retake it for the diff eq portion), in upper division, and in quantum mech. I still don't get all of it. But at least it's not abstract algebra (I hate group theory. ._.)

I confess I hate how much of a slug I feel like right now. I'm awake but bonetired and can't think really straight. Argh.

 

[M3J]

SOMEONE STOP THIS TALK

 

[Gats]

We already do linear algebra at secondary school on my side. I know we have a math culture but I don't think it helps very much that early. I also did some group theory (later), oh my God...It was kinda (just kinda) fun in a way (and it's very gratifying once you solved an exercice) but I clearly was not rigorous enough to continue this. I forgot most of it. Which is quite unsatisfying even though it won't be useful to me.