I suck at math...

JohnRM

JohnRM

Don't make me destroy you
Joined
Apr 18, 2004
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Why can't I understand this?

Write in simplest form.

x+7
----
x² + 4x - 28

problem is that I can't factor the denominator, because there are no multiples of 28 that add up to 4. I don't know what to do, but I know there is something to be done. WTH?


And this...

3x² - 2xy - 1



I also got a word problem I can't figure out how to set up. Just show me how to set this one up. I'd like to try and figure it out myself, from there.

It takes Elizabeth 12 hours to paint a house. It takes Rob 15 hours to paint a house. How long will it take if they paint one together?
 
Unless your last problem is some kind of trick question, assume that Elizabeth paints (1/12) houses per hour and Rob (1/15) houses per hour.

Spoiler Resulting equation :
(1/12)*t + (1/15)*t = 1, with t being the necessary time in hours.

Solve for t.
 
The first one is most probably a typo...... I'm guessing the 4x should read 3x. Then it's very straightforward.

The 2nd one you just rearrange it so that it reads y = .... (all the x's on this side) ...
 
I know a guy called Salvatore that can paint a house in under minute. Just don't say you heard it from me.
 
JohnRM said:
Why can't I understand this?

Write in simplest form.

x+7
----
x² + 4x - 28

problem is that I can't factor the denominator, because there are no multiples of 28 that add up to 4. I don't know what to do, but I know there is something to be done. WTH?
I agree with someone who already posted this but if it is not a typo, the denomonator's x values are either-7.6568 or 3.6568. Please note that they are actually infinantly repeating decimils and are probably something times the square root of a number however I'm not sure what it is. On questions like these, you can use the quadratic equation to find the answer... however if you haven't yet learned the quadratic equation then I would agree that it is probably a typo.

And this...

3x² - 2xy - 1

Like the person below said, isolate the y variable and that's your answer

I also got a word problem I can't figure out how to set up. Just show me how to set this one up. I'd like to try and figure it out myself, from there.

It takes Elizabeth 12 hours to paint a house. It takes Rob 15 hours to paint a house. How long will it take if they paint one together?
Click to expand...

BTW I did these in school a few years ago. They were very hard at the time and I hated learning them. However they are a lot easier once you get some practice in and in hindsight I am glad that I took the time and effort to learn them. Just give them a little time, patience, and effort and soon you will be amazed by the results.
 
By the way, do you know how to find the prime factorization of a number (i.e. 12 is 2*2*3 and 18 is 3*3*2)? This is a very important skill and I wouldn't want to do anything that would prevent you from learning it, however if you already understand the process I have a computer program that I wrote that can find the prime factorization of any number up to (but not including) 1 billion and you are more than welcome to it if you would like it. It doesn't need to be installed, nor does it make any changes to the registry; it just works. I wrote it using C++ to help with my math class as at the time we were having to find the exact value of the square root of numbers on a regular basis and finding the prime factorization is part of the process. It can be a huge time saver in pre algebra and beyond.
 
cool...thread is now stuck in a rat hole where it will never get any responses.

/thread
 
Plus there is a perfectly good maths thread for maths questions already.

EDIT: But Wolfram Alpha is best place to start.
 
@uppi: You lose points for spelling factorise the American way. Next you'll be saying "math".
 
There is absolutely no way that the first question requires you to write this as the answer:
07UNF.gif
 
ParadigmShifter said:
@uppi: You lose points for spelling factorise the American way. Next you'll be saying "math".
Click to expand...

:blush:

Erm...Wolfram Research is an American company, isn't it? I was not sure they would understand proper British English...yeah...that was it. And I blame the spellchecker of my browser...

Seriously, it is hard to settle for one spelling, if half of the stuff you read and write has one spelling and the other half another. About every time a paper is resubmitted to another journal the spelling has to be changed.
 
Mise said:
There is absolutely no way that the first question requires you to write this as the answer:
07UNF.gif
Click to expand...
It gives a slightly better result if you click show steps. It's a matter of manipulating constant terms anyway, you can bunch them together or not as you please. You can put it in the form a/(x+b)+c/(x+d) easily.

And yes, I got the PM. You should have a reply now.
 
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