# Math question one of those challenges your not supposed to get right

Discussion in 'Community' started by wake up Jobs!!!, Aug 27, 2002.

1. ### wake up Jobs!!! macrumors regular

Joined:
Mar 10, 2002
Location:
Miami, Florida
#1
ok my geometry teacher gives us these daily problems to figure out, right out of the SAT and todays problem was kinda midboggleing to me, well here goes

if x+y=3 and x-y=5, what does x squared - y squared =?

thanks

-GaBe-O

2. ### firewire2001 macrumors 6502a

Joined:
Apr 2, 2002
Location:
Hong Kong
#2
x+y=3
x-y=5
--------
2y=-2
y=-1
therefore x=4

so.. x^2+y^2
(4)^2 - (-1)^2
16 - 1
15

-f

 my apologies. [/edit]

3. ### scem0 macrumors 604

Joined:
Jul 16, 2002
Location:
back in NYC!
#3
I took honors alg I last year too. I learned that halfway through the school year. I cant say we are doing hard tuff in geometry this year though.

4. ### wake up Jobs!!! thread starter macrumors regular

Joined:
Mar 10, 2002
Location:
Miami, Florida
#4
thanks smart ass I forgot that with the subtraction orf the y to find out what x equals and then plug it in to find what y equals. As for your sarcasim, this is the second day I have been back in school in 3 months I have totally forgot everything and have not had the time to review. And no I am not asking you how to do my homework, no one said you had to respond moron, I was just looking for some help, seemes like I have found it so I will leave it at that.
Thanks,

-GaBe-O

5. ### King Cobra macrumors 603

Joined:
Mar 2, 2002
#5
>if x+y=3 and x-y=5, what does x squared - y squared =?

Take it from someone who's going into AP Calc.

x+y=3
x-y=5

Using Linear Combination, the y's cancel.

2x=8, x=4

Plug in "x" for one of the equations from the Linear system.

(4)+y=3, y=-1

Substitute "x" and "y" for the last part of the problem. Let the solution = "Q".

(4)^2 - (-1)^2 = Q
16 - 1 = Q
Q = 15

Take it from me, Gabe. I've done some of the toughest non-Calc Math you can think of, and I even know a -little- Calculus. (Ignore firewire2001. He's 13 (or 14) and is being too immature to even act his age.) From personal experience at Pascack Hills (profile) I've helped out all sorts of people in Math, ranging from freshmen to seniors. Algebra is just plug and chug. You just need to know how to cancel out that extra variable.

If you need help with Math you can ask here, or you can PM me or DavPeanut (if that is his name) to help you out.

6. ### Taft macrumors 65816

Joined:
Jan 31, 2002
Location:
Chicago
#6
Dude, harsh. Just remember: what may come easily to you might not be so simple for others. And at some time in our lives we are all challenged.

I aced my college courses in vector analysis (think intro to fluid dynamics) and operating system design, yet I remain humble. Why?? Because for the life of me, I couldn't get above a B- in playwriting.

Here's hoping that you'll run into your humbling experience sooner rather than later.

Taft

7. ### Spaldings macrumors newbie

Joined:
Aug 27, 2002
#7
Looks like you got your x's and y's mixed up here. Your linear combination should have yielded 2x = 8
(for Gabe, this is done by adding different sides of 2 equality statements.

i.e. (x+y) + (x-y) = (3) + (5) giving you the final statement 2x = 8). Solving for x will give you x = 4 which can be substituted into either equation to get y = (-1). This will give you a final answer of 15 for your problem.

A piece of advise for you is that whenever you are manipulating statements like this...plug your answers into the original equations to make sure those statements are still valid. Namely x+y = 3..checks with (4)+(-1) = 3. Verifying the same with the other equation will ensure you are on track. Good luck with your algebra this semester

~s

8. ### Taft macrumors 65816

Joined:
Jan 31, 2002
Location:
Chicago
#8
Heh. I always enjoy seeing newbies come out of the woodwork to help out on these forums. I find the situations that bring out the new posters interesting.

Thats why posting questions here is such a good idea. You never know when a lurker will come out and save the day.

Taft

9. ### sparkleytone macrumors 68020

Joined:
Oct 28, 2001
Location:
Greensboro, NC
#9
omfg you guys choose the dumbest ways to solve equations. i always did hate the way they teach math in school. math makes sense, unless the board of education has anything to say about it.

x + y = 3
x - y = 5

(x + y)(x - y) = x^2 - y^2

:: x^2 - y^2 = 15

10. ### sparkleytone macrumors 68020

Joined:
Oct 28, 2001
Location:
Greensboro, NC
#10
ap geometry??

quit being an *******, he just had a brain fart.

and cobra, don't worry about AP Calc, its a breeze if your teacher isnt dumber than you are.

11. ### oldMac macrumors 6502a

Joined:
Oct 25, 2001
#11
Skinning cats...

Remember, kids...
There's more than one way to get to Fort Wayne.

<script language="JavaScript">
var guessX = 0;
var guessY = 0;
for(guessX=0;guessX-guessY != 5;guessY=(3-guessX)) {
if(guessX - guessY > 5) guessX--;
else guessX++;
}
alert("x=" + guessX + " y=" + guessY);
</script>

12. ### Choppaface macrumors 65816

Joined:
Jan 22, 2002
Location:
SFBA
#12
Re: Skinning cats...

once again brute strength beats brute attitude, eat that AP students and your overinflated dignities

13. ### King Cobra macrumors 603

Joined:
Mar 2, 2002
#13
Ah. Damn, man. I make some of the most [explicit] mistakes you can think of. In first grade there was a contest to see who could completely answer all the questions on a series of Math papers. All at once, my class took page 1, and I was one of the few people in the class, who got even one wrong. [5 + 1 is not = 7. ] Yet, I ended up winning the contest.

Also, the only person faster than me in Math and more accurate than me at the time was my [explicit] 1st grade teacher. This was in a different contest, though.

I'll admit, I answered the problem wrong, but I'm too lazy to double check my work, because I keep making too many [explicit] mistakes.

Spaldings, I'm glad you caught me on that one. I don't usually catch my own mistakes.

oldMac, are you using Mathmatica or some really expensive program like that? I think I'm going to have to use Mathmatica in about 3 years from now, seeing as I will have to take all 3 levels of Calc, plus a course on dy/dx. That'll be fun.

>once again brute strength beats brute attitude, eat that AP students and your overinflated dignities

Easy, big guy.

>(sparkleytone) and cobra, don't worry about AP Calc, its a breeze if your teacher isnt dumber than you are.

I'm sure he isn't. He's also funny. One of his jokes would be what I inserted above.

I did have a teacher in my freshman year, who I had to keep correcting in Earth Science/Astronomy. To make this sound more "out there", he has a Ph. D. Tell me, if a 14 year old (at the time) knows more about something some 40+ year old knows, when he has a doctorate and is teaching Science/Astronomy, what happens to the "doctor" a year later? He gets fired. True story.

Just give me a second chance on these Math problems. I'll recheck my work, unlike a few here.

14. ### mmmdreg macrumors 65816

Joined:
Apr 14, 2002
Location:
Sydney, Australia
#14
that's not exactly complicated..I looked at it found x and y in 5 seconds iny my head and then did the rest straight away...

15. ### Mr. Anderson Moderator emeritus

Joined:
Nov 1, 2001
Location:
VA
#15
just wait till some of you 'math whizzes' get to college and have to take Differential Equations - that was fun! And makes this stuff look like 1+1 - but I'm not knocking it, you need to learn the Algebra - especially if you ever plan on doing anything technical.

I'm really amazed at all the different solutions everyone came up with, its quite entertaining.

D

16. ### sparkleytone macrumors 68020

Joined:
Oct 28, 2001
Location:
Greensboro, NC
#16
i seem to gain a reputation in all my math classes of finding the most backasswards ways of solving things. but things just make sense to me. my calculus teacher in HS used to love me going to the board, because no one ever got the answer like i did.

as far as college math goes...im not at a math oriented school, and i took calc III my freshman first semester. the teacher was absolutely horrid and i dropped quicklike. since then i stay away from that building, and being that I got a 5 on my AP Calc exam, I don't have any math requirements to fill for my degree (vocal performance).

17. ### sparkleytone macrumors 68020

Joined:
Oct 28, 2001
Location:
Greensboro, NC
#17
oh, and those that are math whizzes, do yourself a favor and take AP Music Theory. It's a great class and math skills are quite useful in it. Theory rocks.

18. ### awrc macrumors regular

Joined:
Apr 20, 2002
Location:
Milwaukee, WI
#18
College level math. I shudder. I don't know how it compares to what's taught in US universities, but I did a couple of years of math when I was doing my degree at Edinburgh University. Although I was a CS major, scheduling problems meant that I ended up in the 2nd year "Engineering Mathematics" class rather than the easier course that contained only the stuff we really needed to know.

I pitied those engineers. Since UK universities tend to specialize a lot more than in the US (none of this "well rounded" stuff - for the third and fourth years of my degree I did nothing but CS courses) they had to cram all the math the engineers would ever need into two years. That was one tough course - probably the 2nd toughest class I did in my entire time at university (the toughest was the 3rd year course in Computability, which I failed spectacularly and which probably cost me a 1st).

What I hated most about math - and I think this applied from high school right until the very end - was that they'd spend weeks giving you ever-more difficult examples of, say, differential equations, until eventually you hit a brick wall with problems that you just couldn't solve. Then they'd show you a new technique that not only made it possible to solve, but made all the stuff you'd spent weeks working on ten times easier to do.

19. ### jelloshotsrule macrumors G3

Joined:
Feb 7, 2002
Location:
serendipity
#19
just go to art school. most arts don't require any math knowledge..

seems the best way to go to me...

20. ### krossfyter macrumors 601

Joined:
Jan 13, 2002
Location:
secret city
#20
yep jellos right be an aritist no math is required. its great.

math is a part of the axis of evil...

i think thats what George Bush said.

21. ### diorio macrumors 6502a

Joined:
Aug 22, 2002
#21
You should ask your math teacher, not a bunch of people who probably havn't done that stuff for twenty years.

22. ### sparkleytone macrumors 68020

Joined:
Oct 28, 2001
Location:
Greensboro, NC
#22
just go to arts school huh?

just make sure you have some friggin' talent.

23. ### krossfyter macrumors 601

Joined:
Jan 13, 2002
Location:
secret city
#23

actually ive seen some people there that one can question thier talent and question why they ever got in at all. i mean its a trip... some go because they think its easy and they get to draw or paint landscapes and flowers all day. heh.
makes for some entertainment. but yeah for the most part one must have some skills already.

24. ### mymemory macrumors 68020

Joined:
May 9, 2001
Location:
Miami
#24
Kids,
After reading all this math stuff I'm realizing how gratefull I am right now, every time farder and farder from those teen age years. I still don't get it any math stuff, my brain is not prepared yet and I'm so glad I do not have to face that again until I have kid of your age (about 20 year from now at list).

I love life without school

25. ### wake up Jobs!!! thread starter macrumors regular

Joined:
Mar 10, 2002
Location:
Miami, Florida
#25
Thanks guys, for all your help . I had a brain fart if you want to call it that. After reading what king cobra wrote I realized that i did learn this last year in Alg, but since it was the begining of the year when I learned it, and the fact that I havent used my thinking part of my brain for about three months , I forgot it. Now I remeber that and alot more that I thought I forgot from last year. This is what happens when all you do is sleep over the summer. On a more positive note, I was asked to join the JV football team by the coach today because they were in need of O-linemen, he said I could even start I hope