ForumsWEPR0 is the largest number

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Einfach
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Einfach
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Nomad

http://i1124.photobucket.com/albums/l577/gemcrafteinfach/0largestnumber.png

This graph, shown above, is the graph:
y=-1/x
This graph covers the values of all rational numbers (except for 0).

Its derivative (the slope of the tangent line at that particular point) is y=1/x^2, a graph which, for all rational numbers, has a positive y-value, meaning the graph is constantly increasing in value.

As x increases, y constantly increases in value, and y covers all rational numbers. As x approaches infinity, y gets closer and closer to 0. One may logically conclude that 0, therefore, is the largest real number.

One may argue that you are excluding the value x=0, because that cannot be said to have a definitive y-value value at that x-value.. However, look at the derivative, which is 1/x^2. As x approaches 0 in the derivative, y approaches infinity, regardless if you take a positive or negative 0. Therefore, at x=0, the value must be increasing, whatever the corresponding value of y is.

Discuss...

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Xzeno
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Xzeno
2,301 posts
Nomad

One may logically conclude that 0, therefore, is the largest real number.
Non sequitur. The values of X and Y don't alter the value of 0.

-1 < 0 < 1.
Einfach
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Einfach
1,448 posts
Nomad

Non sequitur. The values of X and Y don't alter the value of 0.

-1 < 0 < 1.


Yes, it does follow. This graph is constantly increasing, as shown by its derivative, and it covers all real numbers; thus, 0 must be the greatest number.
Graham
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Graham
8,051 posts
Nomad

0 is the absence of a number.

driejen
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driejen
486 posts
Nomad

Its derivative (the slope of the tangent line at that particular point) is y=1/x^2, a graph which, for all rational numbers, has a positive y-value, meaning the graph is constantly increasing in value.


The value of y isn't necessarily positive at x=0, as y=1/0. At x=0 the value of increase is undefined thus one cannot conclude that the value of y after x=0 is greater than before x=0.
nichodemus
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nichodemus
14,991 posts
Grand Duke

So you're saying based on an asymptote that 0 is the largest number?

driejen
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driejen
486 posts
Nomad

One may argue that you are excluding the value x=0, because that cannot be said to have a definitive y-value value at that x-value.. However, look at the derivative, which is 1/x^2. As x approaches 0 in the derivative, y approaches infinity, regardless if you take a positive or negative 0. Therefore, at x=0, the value must be increasing, whatever the corresponding value of y is.

Sorry missed this bit.

As x approaches 0 in the derivative, y approaches infinity

When you divide by x, as x approches 0, y approaches not only infinity, but negative infinity as well. Just take a look at the original graph of y=-1/x. When x=0, y=infinity AND y=-infinity. One can also argue that y is also equal to everything in between, hence y is undefined at that point so it is incoherent to argue that it is therefore a positive value.
Einfach
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Einfach
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Nomad

[quote]As x approaches 0 in the derivative, y approaches infinity


When you divide by x, as x approches 0, y approaches not only infinity, but negative infinity as well. Just take a look at the original graph of y=-1/x. When x=0, y=infinity AND y=-infinity. One can also argue that y is also equal to everything in between, hence y is undefined at that point so it is incoherent to argue that it is therefore a positive value.[/quote]

Notice - the derivative of y = -1/x is 1/x^2.

The derivative is the slope of the tangent line, and so the slope of the tangent line at x=0 is infinity, or the limit as x approaches 0 of 1/x^2 is positive infinity, whether you take the positive or negative values of 0. Thus, the values are increasing according to the derivative; therefore, the value of the numbers after 0 is greater than before 0.

Thus, 0 is the largest number.
Moe
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Moe
1,714 posts
Blacksmith

The derivative is the slope of the tangent line, and so the slope of the tangent line at x=0 is infinity, or the limit as x approaches 0 of 1/x^2 is positive infinity,


No, the slope of the tangent line would be undefined, not infinity.
Sonatavarius
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Sonatavarius
1,322 posts
Farmer

0 = 0.... where a line crosses the x or y axis @ 0 is irrelevant.

plus, as graham said 0 = the absence of value...0 is just how we represent that concept

Einfach
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Einfach
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Nomad

No, the slope of the tangent line would be undefined, not infinity.


A way to get around this - don't divide by 0; use the limit.

Lim (1/x^2)
x --> 0
Einfach
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Einfach
1,448 posts
Nomad

= infinity

driejen
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driejen
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Nomad

I don't think you've addressed my point. You are assigning 1/0 a value of infinity when it is infact undefined. You cannot assume a value for y at x=0 because dividing by zero is not a legitimate operation. By dividing by zero you can 'rove' that 1=2 and the like.

Even if an aymptote leans towards a value and suggests a solution to dividing by zero, it has no solution. You cannot tell what the value at x=0 actually is.

What I am trying to point out in the asymptote of the original graph y=-1/x is that when dividing by zero, you can get not only infinity but negative infinity as well just by looking at the graph. Thus -1/0=infinity and -infinity
Even if you say that the derivative is 1/x^2 and not -1/x, then you are saying that 1/0=infinity but not negative infinity? Why not? For if -1/x=infinity and -infinity, then it follows that 1/x=-infinity and infinity.

For you to assume that the value only keeps increasing, then are you not in turn saying that infinity is equal to negative infinity? As I see it, at x=0, the value of y decreases from infinity to negative infinity. But since both of these values lie on x=0, it follows that the value of y also increases from negative infinity to infinity.

Einfach
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Einfach
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Nomad

plus, as graham said 0 = the absence of value...0 is just how we represent that concept


Nothing is something.
driejen
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driejen
486 posts
Nomad

Lim (1/x^2)
x --> 0


You do realise that this shows that the limit to the right is infinity but the limit to the left is negative infinity right? Hence it is undefined. Heres quick link; [url=http://en.wikipedia.org/wiki/Division_by_zero]
Einfach
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Einfach
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Nomad

I don't think you've addressed my point. You are assigning 1/0 a value of infinity when it is infact undefined. You cannot assume a value for y at x=0 because dividing by zero is not a legitimate operation. By dividing by zero you can 'rove' that 1=2 and the like.


But we're using the limit - not actually dividing by 0.

Even if an aymptote leans towards a value and suggests a solution to dividing by zero, it has no solution. You cannot tell what the value at x=0 actually is.


Limits

What I am trying to point out in the asymptote of the original graph y=-1/x is that when dividing by zero, you can get not only infinity but negative infinity as well just by looking at the graph. Thus -1/0=infinity and -infinity


We get around this by using the limit of the derivative, which is infinity whether you take the positive or negative side of 0.

Even if you say that the derivative is 1/x^2 and not -1/x, then you are saying that 1/0=infinity but not negative infinity? Why not? For if -1/x=infinity and -infinity, then it follows that 1/x=-infinity and infinity.


What is (0.000000000000...1)^2? A positive number.
What is (-0.00000000000...1)^2? A positive number.

So a positive divided by a positive = a positive, right, so either way, it's a positive infinity.

For you to assume that the value only keeps increasing, then are you not in turn saying that infinity is equal to negative infinity? As I see it, at x=0, the value of y decreases from infinity to negative infinity. But since both of these values lie on x=0, it follows that the value of y also increases from negative infinity to infinity.


No, because we're getting around negative infinity. There is no negative infinity in the derivative.

You do realise that this shows that the limit to the right is infinity but the limit to the left is negative infinity right? Hence it is undefined. Heres quick link; [url=http://en.wikipedia.org/wiki/Division_by_zero]


See above...
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