THE MATH THREAD

[controller]

the equations is

 

(1/x)+(1/(x+4))=(1/3)

 

i'm totally brainfarting on how to do this.  anyone of you geniuses willing to help me?

[Chuckie]

^^-1

[Croix]

Assuming you need to find what X is, it's 1±√13. I'm not really sure if that's what you're looking for though.

[Dahaka]

ur mum

[Archonic]

Bro.  Bro.  Bro.  It's the weekend.  No time for this.  It's the time to let your brain rot *DRY HUMPING* PokeMMO for 10 hours straight and PRETEND to do homework.

 

[spoiler](Actually has no idea how to do this.)[spoiler]jk, knows how do to this just too lazy[/spoiler][/spoiler]

[kloneman]

playing PokeMMO

pls go

[Archonic]

pls go

 

nu.  

 

*edits to say dry humping*

 

[spoiler]cuz sex.[/spoiler]

[DiverMatt]

[color=red]*DISCLAIMER - I HAVE HAD 2 MARGARITAS AND 2 NEAT SCOTCHES SO THIS IS DRUNK MATH*[/color]

 

(1/x) + (1/(x+4)) = 1/3

* x

1 + (x/(x+4) = x/3

*(x+4)

x + 4 + x = (x^2 + 4x)/3

*3

3x + 12 + 3x = x^2 + 4x

6x + 12 = x^2 + 4x

12 = x^2 - 2x

0 = x^2 - 2x - 12

0 = (x-4.6)(x+ 2.6)

x = -2.6, 4.6

[Croix]

*DISCLAIMER - I HAVE HAD 2 MARGARITAS AND 2 NEAT SCOTCHES SO THIS IS DRUNK MATH*
 
(1/x) + (1/(x+4)) = 1/3
* x
1 + (x/(x+4) = x/3
*(x+4)
x + 4 + x = (x^2 + 4x)/3
*3
3x + 12 + 3x = x^2 + 4x
6x + 12 = x^2 + 4x
12 = x^2 - 2x
0 = x^2 - 2x - 12
0 = (x-4.6)(x+ 2.6)
x = -2.6, 4.6

(1/x)+(1/(x+4))=(1/3) Solve for x.

Bring (1/(x+4)) + (1/x) together using the common denominator x(x+4):

 

Cross multiply:

6 (2 + x) = x (4 + x)

 

Expand out terms of the left hand side:

12 + 6x = x (4 + x)

 

Expand out terms of the right hand side:

12 + 6x = 4x + x^2

 

Subtract x^2+4x from both sides:

12 + 2x - x^2 =0

Multiply both sides by -1:

-12 - 2x + x^2 = 0

 

Add 12 to both sides:

-2x + x^2 = 12

 

Add 1 to both sides:

1 - 2x + x^2 = 13

 

Write the left hand side as a square:

(-1 + x)^2 = 13

 

Take the square root of both sides:

-1 + x = √13 or -1 + x = -√13

 

Add 1 to both sides:

x = 1 + √13 or x = 1 - √13

 

In other words:

1±√13

[JWingWangWong]

Croix is a smart cookie

[lillyfly]

it's too late for math....

[Croix]

Croix is a smart cookie

It's basic pre-calculus. It's not a big deal.

[Dannnno]

Lets make this the math problem megathread.

We have two variables a and b.

Let a = b, then a^2 = b^2.
This means a^2-b^2=0.

Factoring the left yields (a-b)(a+b)=0.

This means (a-b)(a+b)=a^2-b^2.

But since b=a, You can say that a^2-b^2 = a*b-b^2.

Therefore (a-b)(a+b)=a*b-b^2.

Factoring the right yields b*(a-b).

Therefore (a-b)(a+b)=b*(a-b).

Dividing by a-b gives a+b=b.

But since a=b, we have b+b=b, or 2b=b.

Dividing by b gives 2=1.

This seems legit (it isn't) at first glance. Who here can tell me what is wrong with this

 

I'll give you a hint - at some point they divided by zero. 

dividing by zero is a nono

[Croix]

Who here can tell me what is wrong with this

Me being awake. Good night.

[Tranzmaster]

Lets make this the math problem megathread.

We have two variables a and b.

Let a = b, then a^2 = b^2.
This means a^2-b^2=0.

Factoring the left yields (a-b)(a+b)=0.

This means (a-b)(a+b)=a^2-b^2.

But since b=a, You can say that a^2-b^2 = a*b-b^2.

Therefore (a-b)(a+b)=a*b-b^2.

Factoring the right yields b*(a-b).

Therefore (a-b)(a+b)=b*(a-b).

Dividing by a-b gives a+b=b.

But since a=b, we have b+b=b, or 2b=b.

Dividing by b gives 2=1.

This seems legit (it isn't) at first glance. Who here can tell me what is wrong with this

 

I'll give you a hint - at some point they divided by zero. 

dividing by zero is a nono

 

 

"Dividing by a-b gives a+b=b."

 

This is the error in the argumentation.

 

Since a = b, you're dividing by zero. Dividing left and right by zero makes it really easy to solve equations ;)

[Dannnno]

"Dividing by a-b gives a+b=b."

 

Since a = b, you're dividing by zero. Dividing left and right by zero makes it really easy to solve equations ;)

 

Ding ding ding!  Did you know this was actually provided as a 'proof' in math textbooks for a time? 

 

EDIT: Heres one from an older textbook of mine

Let F be a vector field on U, and let C be a curve in U. The dot product F(C(T))*dC/dT is a function of t.

Let F(x,y) = (x/r^3, y/r^3) and where r = (x^2+y^2)^(1/2). Find the integral of F along the curve C(t) = ((e^t)*(cos t), (e^t)*(sin t)) from the point (1,0) to the point (e^2pi,0).

Have fun!

Edited September 2, 2013 by Dannnno

[Tranzmaster]

Ding ding ding!  Did you know this was actually provided as a 'proof' in math textbooks for a time? 

 

Hmm interesting.

 

Also, I'm for a math problem megathread ;)

[AstroSpud]

I got a hard one for you.
[spoiler]
If 3X=15, what is X?
[/spoiler]

[lillyfly]

I got a hard one for you.
[spoiler]
If 3X=15, what is X?
[/spoiler]

5

 

[spoiler] I had to pull out a calculator, no joke [/spoiler]

[Dannnno]

Hmm interesting.

 

Also, I'm for a math problem megathread ;)

 

 

EDIT: Heres one from an older textbook of mine

Let F be a vector field on U, and let C be a curve in U. The dot product F(C(T))*dC/dT is a function of t.

Let F(x,y) = (x/r^3, y/r^3) and where r = (x^2+y^2)^(1/2). Find the integral of F along the curve C(t) = ((e^t)*(cos t), (e^t)*(sin t)) from the point (1,0) to the point (e^2pi,0).

Have fun!

[lillyfly]

I'll give a sequence problem, because I kind of remember doing these.
(v)= sub [as in under, for those that don't know. I don't know how to type a sub)

a(v)n= 5/2(-.5)^n-1     Find the first 5 terms
 

[CipherWeston]

So if this is turning into a math megathread, can I post my Calc 2 questions when I don't understand them?

[HelenaVillagra]

Someone help me solve this ODE at the point (1,0).

I'm doing something wrong or the point (1,0) doesn't belong to the ODE regions?   -_- 

[Chuckie]

So if this is turning into a math megathread

 

better get Atuan on the scene.

[heyimacrab]

Wow you guys are so dumb lol how can you not know how to do this easy stuff. Its so easy .

 

(1/x)+(1/(x+4))=(1/3)

 

1 out of x is equal to greater than 1 out of 3 but 1 out of x plus 4 is also equal to 1 out of 3. So all you gotta do is find out what 1 out of 3 is. 1 out of 3 is in a parenthesis so obviously everybody knows what that means,you obviously dont count the number. Its like whne you type a sentence in parenthesis but it actually doesnt exist because nobody reads it. And when you read out loud in school your not really sure if you should actually read the parenthesis part out loud or not. Sometimes you actually say the word parenthesis than read the sentene inside the parenthesis because you think thats what you should do.But i never do that because it feels so forced I dont like to try too hard. I hate kidswho tried to hard to read good out loud to the class . Its not like im gonna remember you when school is over like " oh john yeah that guy was a great reader". He could be the president of america and I still wouldnt think about him, so why would I care about that guy if he reads good.