#1
I tried finding that last thread about a similar subject. My teacher showed this problem and I can't figure it out.

Bear in mind:
2^2= 2+2
3^2= 3+3+3
4^2= 4+4+4+4
etc.

Therefore, we can say:
n^2= n+n+n+n+n... n times, right?

Now, we take the derivative of that:
2n= 1+1+1+1+1... n times.
2n=n.
Therefore, 2=1.

I'm sure there's a problem here, but I can't find it.
#3
yes 2=1, whatever you say...
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#7
no, 2n=n+n, so where n is one, 2=2
if you meant n^2,
then, where n is one,
n^2=1 (n+, n times)
so n is still 1
Quote by soulflyV
Quote by Xplozive
Once I was pissing in the kitchen sink when I'd had a few and my friend walked in and goes wtf.

Once I was pissing in my friend when a few had I'd and my sink wtf goes in and walked.
#8
i havent done this in 2 years or so, but if u take the derivitive of a number (say 5), it goes away doesnt it?

if it does (i dont really remember), then the deritive of n^2= n+n+n+n+n would not be 2n=1+1+1+1+1....
dude, what about an actual solo in death metal instead of that poof from linkin park. Think of Pulse of the Maggots - Bed Of Razors


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#11
n is a constant not a variable hence


0=0

EDIT: Basicly n is just a number and you can't differentiate with respect to a constant (i think ?), and if you differentiated wrt a variable say x you'd get 0.


If n was a variable

n ^2=n.n

diff wrt n

using product rule

(Vdu+Udv)

2n=n.1+n.1

2n=2n
#13
Quote by The2abraxis
i havent done this in 2 years or so, but if u take the derivitive of a number (say 5), it goes away doesnt it?

if it does (i dont really remember), then the deritive of n^2= n+n+n+n+n would not be 2n=1+1+1+1+1....

n is a variable; that's why the derivative of n^2 is 2n. This is also why the derivative of n is 1.

If n was a variable

n ^2=n.n

diff wrt n

using product rule

(Vdu+Udv)

2n=n.1+n.1

2n=2n

I understand it this way, but n.n is the same as n+n+n... n times.
Last edited by tylerishot at May 25, 2008,
#17
Quote by tylerishot
n is a variable; that's why the derivative of n^2 is 2n. This is also why the derivative of n is 1.



its not a very applicable variable it seems. because if u plug in 5^2=5+5+5+5+5
and took the derivitve, the 5's on the right hand side would not be equal to 1
dude, what about an actual solo in death metal instead of that poof from linkin park. Think of Pulse of the Maggots - Bed Of Razors


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#18
Quote by that_1_dude24
No, 2n =/= n, unless it is zero.


Exactly

the graph is y = 2^2

2^2 = 4 = constant

The gradient of this graph = 0

The 1st derivative of this graph also must = 0

2n = n = 0

Its just a stupid trick
#19
Quote by The2abraxis
its not a very applicable variable it seems. because if u plug in 5^2=5+5+5+5+5
and took the derivitve, the 5's on the right hand side would not be equal to 1

If you take the derivative of 5^2=5+5+5+5+5, it's 0=0. Just so you know.
#20
the only one of these that works is:
Say 0.9 recurring is y.
so y x 10, ie. 10y = 9.9 recurring
10y - y = 9y = 9.9 recurring - 0.9 recurring = 9
so 9y = 9
divide by 9
y=1
therefore, 0.9 recurring is equal to 1
Quote by soulflyV
Quote by Xplozive
Once I was pissing in the kitchen sink when I'd had a few and my friend walked in and goes wtf.

Once I was pissing in my friend when a few had I'd and my sink wtf goes in and walked.
#21
Quote by tylerishot
If you take the derivative of 5^2=5+5+5+5+5, it's 0=0. Just so you know.


well there ya go :-D
dude, what about an actual solo in death metal instead of that poof from linkin park. Think of Pulse of the Maggots - Bed Of Razors


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#22
Quote by plastercaster
the only one of these that works is:
Say 0.9 recurring is y.
so y x 10, ie. 10y = 9.9 recurring
10y - y = 9y = 9.9 recurring - 0.9 recurring = 9
so 9y = 9
divide by 9
y=1
therefore, 0.9 recurring is equal to 1

10y isn't 9.99999 recurring.
It's 9.99999....9990.
Just so you know.

EDIT: And because I know you won't take my word for it, look at it this way:
Say y=0.9.

Therefore, 2y=1.8
3y=2.7
4y=3.6
etc.

if y=0.9999...
2y=1.999999....98
3y=2.999999...97
etc.
It's a stupid problem.
Last edited by tylerishot at May 25, 2008,
#23
So you're saying if I have two apples, I really only have one?

Mind blooooowwwwing.....
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#24
Quote by tylerishot
I tried finding that last thread about a similar subject. My teacher showed this problem and I can't figure it out.

Bear in mind:
2^2= 2+2
3^2= 3+3+3
4^2= 4+4+4+4
etc.

Therefore, we can say:
n^2= n+n+n+n+n... n times, right?

Now, we take the derivative of that:
2n= 1+1+1+1+1... n times.
2n=n.
Therefore, 2=1.

I'm sure there's a problem here, but I can't find it.

you're wrong already. 2^2= 2x2
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#26
Quote by LazyLatinoRocke
you're wrong already. 2^2= 2x2

yes, but if you try it in the pattern he had it in, it works. 2^2=4 2+2=4. 4=4.
Quote by tylerishot
10y isn't 9.99999 recurring.
It's 9.99999....9990.
Just so you know.

EDIT: And because I know you won't take my word for it, look at it this way:
Say y=0.9.

Therefore, 2y=1.8
3y=2.7
4y=3.6
etc.

if y=0.9999...
2y=1.999999....98
3y=2.999999...97
etc.
It's a stupid problem.

Technically, you can't divide or multiply irrational numbers, because they have no end. They're meaningless.
Last edited by that_1_dude24 at May 25, 2008,
#27
ya the best argument may be that n cant be applied as a variable
dude, what about an actual solo in death metal instead of that poof from linkin park. Think of Pulse of the Maggots - Bed Of Razors


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#28
Quote by tylerishot
10y isn't 9.99999 recurring.
It's 9.99999....9990.
Just so you know.

EDIT: And because I know you won't take my word for it, look at it this way:
Say y=0.9.

Therefore, 2y=1.8
3y=2.7
4y=3.6
etc.

if y=0.9999...
2y=1.999999....98
3y=2.999999...97
etc.
It's a stupid problem.

I think you're missing the point of recurring numbers.
you're thinking in finite terms, your logic only works with a large but not infinite number of .9s. It is mathematically accepted that 0.9 recurring is equal to 1.
Quote by soulflyV
Quote by Xplozive
Once I was pissing in the kitchen sink when I'd had a few and my friend walked in and goes wtf.

Once I was pissing in my friend when a few had I'd and my sink wtf goes in and walked.
#29
Just look at it this way, 2, does not equal 1.Period. There you go, problem solved.
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#30
Quote by tylerishot


Therefore, we can say:
n^2= n+n+n+n+n... n times, right?

Now, we take the derivative of that:
2n= 1+1+1+1+1... n times.
2n=n.
Therefore, 2=1.

I'm sure there's a problem here, but I can't find it.


when you say n times, that is a constant

derivative of (2n) = derivative of a (sum of a sequence of terms)
0 = 0
#32
he said that not too many posts before (that 0=0)
dude, what about an actual solo in death metal instead of that poof from linkin park. Think of Pulse of the Maggots - Bed Of Razors


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