View Full Version : Solve for x

Peegee

11-10-2010, 04:00 PM

(quiet, asians)

http://i54.:bou::bou::bou::bou::bou::bou::bou::bou::bou::bou::bou::bou:/2euic2f.jpg

x-7 = 19+x

x^2 -7x = 19x + x^2

subtract 19x+x^2 from both sides

-7x - 19x = 0

x = 0 QED

qwertysaur

11-10-2010, 04:46 PM

Incorrect. If you substitute x = 0 then you will get -7 = 19 which is wrong. The correct answer is no solution.

Proof

<pre>

x-7 = 19 + x

-x -x</pre>

-7 = 19, a contradiction indicating no solution.

You can see the fallacy in your work because ito get x=0 you had to multiply everything by x. However assume x is 0 you are simply multiplying everything by zero and all information is lost.

Peegee

11-10-2010, 04:57 PM

Incorrect. If you substitute x = 0 then you will get -7 = 19 which is wrong. The correct answer is no solution.

Proof

<pre>

x-7 = 19 + x

-x -x</pre>

-7 = 19, a contradiction indicating no solution.

You can see the fallacy in your work because ito get x=0 you had to multiply everything by x. However assume x is 0 you are simply multiplying everything by zero and all information is lost.

but I added and mutiplied everything on both sides. Ergo it is valid. x = 0

Hollycat

11-10-2010, 04:58 PM

correct, x=nrn

NorthernChaosGod

11-10-2010, 05:01 PM

Incorrect. If you substitute x = 0 then you will get -7 = 19 which is wrong. The correct answer is no solution.

Proof

<pre>

x-7 = 19 + x

-x -x</pre>

-7 = 19, a contradiction indicating no solution.

You can see the fallacy in your work because ito get x=0 you had to multiply everything by x. However assume x is 0 you are simply multiplying everything by zero and all information is lost.

This, you can see it without doing any work.

but I added and mutiplied everything on both sides. Ergo it is valid. x = 0

It's only valid if you plug it back in and get a valid result. :p

Peegee

11-10-2010, 05:03 PM

I thought I told you guys NO ASIANS

Raistlin

11-10-2010, 05:09 PM

Apparently "asians" are anyone who knows anything about math.

Speaking of which, we haven't had a "does 0.999... = 1?" thread in a while.

NorthernChaosGod

11-10-2010, 06:03 PM

Speaking of which, we haven't had a "does 0.999... = 1?" thread in a while.

Why would you want to do that again? :|

Hollycat

11-10-2010, 06:17 PM

I thought I told you guys NO ASIANS

racist

Raistlin

11-10-2010, 06:23 PM

Speaking of which, we haven't had a "does 0.999... = 1?" thread in a while.

Why would you want to do that again? :|

Because the people who refuse to accept it are always entertaining. And math is fun.

Peegee

11-10-2010, 06:43 PM

Speaking of which, we haven't had a "does 0.999... = 1?" thread in a while.

Why would you want to do that again? :|

Because the people who refuse to accept it are always entertaining. And math is fun.

Regardless I'm correct. x = 0 and 26 = 0 . But x != 26 that would be a fallacy.

qwertysaur

11-10-2010, 07:20 PM

Incorrect. If you substitute x = 0 then you will get -7 = 19 which is wrong. The correct answer is no solution.

Proof

<pre>

x-7 = 19 + x

-x -x</pre>

-7 = 19, a contradiction indicating no solution.

You can see the fallacy in your work because ito get x=0 you had to multiply everything by x. However assume x is 0 you are simply multiplying everything by zero and all information is lost.

but I added and mutiplied everything on both sides. Ergo it is valid. x = 0

If you want to prove that x = 0, then you can't multiply both sides of the equation by x to get that solution, because it will always result in 0 = 0. (Side note you also can't divide by x to prove x = 0 because dividing by zero results in no solution.) Take for example x+1 = 2. It should be obvious that x = 1, but lets go with pg's method. Multiply everything by x to get x<sup>2</sup>+x = 2x. Subtract 2x from both sides and you get x<sup>2</sup>-x = 0. Factor and you have (x)(x-1) = 0, giving the solutions x=0 and x=1. However, if x=0 then you get 1 = 2 which is a contradiction.

There are many problems where you have to reject a solution because an answer makes no sense. For example you have a rectangle where the length of one side is three units less than that of the other, and the area is found to be 4 square units. You get (x)(x-3) = 4, which becomes x<sup>2</sup>-3x = 4. Subtract 4 form both sides to get x<sup>2</sup>-3x-4 = 0. Factor to get (x-4)(x+1) = 0. So x = 4 or x = -1. You have to reject x = -1 because you can't have a side with negative length.

Remember to always check to make sure your solutions actually make sense. Also when using an esoteric process for finding the solution, make sure there is no way that is easier first. Don't use calculus to find the area of a circle, just use A = πr<sup>2</sup>. The calculus method is possible, but much more time consuming.

Peegee

11-10-2010, 07:32 PM

Incorrect. If you substitute x = 0 then you will get -7 = 19 which is wrong. The correct answer is no solution.

Proof

<pre>

x-7 = 19 + x

-x -x</pre>

-7 = 19, a contradiction indicating no solution.

You can see the fallacy in your work because ito get x=0 you had to multiply everything by x. However assume x is 0 you are simply multiplying everything by zero and all information is lost.

but I added and mutiplied everything on both sides. Ergo it is valid. x = 0

If you want to prove that x = 0, then you can't multiply both sides of the equation by x to get that solution, because it will always result in 0 = 0. (Side note you also can't divide by x to prove x = 0 because dividing by zero results in no solution.) Take for example x+1 = 2. It should be obvious that x = 1, but lets go with pg's method. Multiply everything by x to get x<sup>2</sup>+x = 2x. Subtract 2x from both sides and you get x<sup>2</sup>-x = 0. Factor and you have (x)(x-1) = 0, giving the solutions x=0 and x=1. However, if x=0 then you get 1 = 2 which is a contradiction.

There are many problems where you have to reject a solution because an answer makes no sense. For example you have a rectangle where the length of one side is three units less than that of the other, and the area is found to be 4 square units. You get (x)(x-3) = 4, which becomes x<sup>2</sup>-3x = 4. Subtract 4 form both sides to get x<sup>2</sup>-3x-4 = 0. Factor to get (x-4)(x+1) = 0. So x = 4 or x = -1. You have to reject x = -1 because you can't have a side with negative length.

Remember to always check to make sure your solutions actually make sense. Also when using an esoteric process for finding the solution, make sure there is no way that is easier first. Don't use calculus to find the area of a circle, just use A = πr<sup>2</sup>. The calculus method is possible, but much more time consuming.

oh EoFF :love:

ps aren't you aznnnn?

escobert

11-10-2010, 07:33 PM

math is for losers.

Peegee

11-10-2010, 07:40 PM

math is for losers.

and bert. asl?

qwertysaur

11-10-2010, 08:22 PM

I'm not AZN pg :p

Peegee

11-10-2010, 08:54 PM

I'm not AZN pg :p

Yet you did math. QED

Shlup

11-10-2010, 09:02 PM

Aww, I was hoping you were posting a real equation for me to solve. I miss algebra. ;_;

Mirage

11-10-2010, 09:12 PM

I consider 0 = 26 a completely valid answer. Just as valid as for example "tuesday".

Peegee

11-10-2010, 09:13 PM

Aww, I was hoping you were posting a real equation for me to solve. I miss algebra. ;_;

It is a real equation.

Fine here's another:

x-7 = x+9 . Solve for x.

Raistlin

11-10-2010, 09:16 PM

X is obviously a quantum number without a fixed value.

Peegee

11-10-2010, 09:55 PM

X is obviously a quantum number without a fixed value.

now now we don't need to be mean. Stephen Hawking already established that everything in the past exists in simultaneously plausible possibility until it is measured.

So x is whatever we determine it to be now, and the past will adapt to our fiction. Christianity 1, atheists 0

Hollycat

11-10-2010, 10:01 PM

x is whatever you want it to be, I think its chocolate mint ice cream with butterfinger sprinkled on top, next to seasons 1-8 of Monk on dvd

Mirage

11-10-2010, 10:24 PM

I already established that x = tuesday. Stop spreading misinformation.

oh btw

which anime is that from?

rubah

11-11-2010, 01:55 AM

that's cool, qwerty. I was trolling PGies when I gave him the x=0 proof, but your posts are pretty interesting!

NorthernChaosGod

11-11-2010, 02:05 AM

I hate you for spitting in the face of basic algebra, PG.

Shlup

11-11-2010, 02:10 AM

I consider 0 = 26 a completely valid answer. Just as valid as for example "tuesday".

http://i194.photobucket.com/albums/z108/btbrian14/Gifs/Reaction/ColbertNoWay-1.gif

Peegee

11-11-2010, 03:45 AM

that's cool, qwerty. I was trolling PGies when I gave him the x=0 proof, but your posts are pretty interesting!

Rodarian

11-11-2010, 06:33 AM

I use to love maths..Right up till grade ten...I got a horrible math teacher that belittle me if I got it wrong....

After that I stopped liking math...

Now I'm just a dumb purazn... :(

Mirage

11-11-2010, 11:50 AM

I consider 0 = 26 a completely valid answer. Just as valid as for example "tuesday".

Image

What do you mean? Please elaborate. I bet that guy isn't even a real teacher, so how would he know?!

Shlup

11-11-2010, 03:59 PM

Stephen Colbert knows everything. Especially America things. Like maths.

Alive-Cat

11-11-2010, 05:36 PM

Okay, okay, guys, I come clean. I am x. :)

NorthernChaosGod

11-11-2010, 06:34 PM

Okay, okay, guys, I come clean. I am x. :)

I found x!

Alive-Cat

11-11-2010, 06:58 PM

NorthernChaosGod wins the thread!

Peegee

11-11-2010, 08:00 PM

NorthernChaosGod wins the thread!

What are you 12? asl op

NorthernChaosGod

11-12-2010, 01:26 AM

NorthernChaosGod wins the thread!

What are you 12? asl op

Have a seat over there.

Peegee

11-12-2010, 07:55 PM

NorthernChaosGod wins the thread!

What are you 12? asl op

Have a seat over there.

No. You're not my mommy

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