Maze1125 said:
infinity + 1 = infinity
There's absolutely nothing wrong with him producing that extra 1, infinity is such that it allows that.
Not true, infinity + 1 does in fact equal infinity, however the second infinity is greater than the infinity used first.
To use overly complicated mathematics to prove something conceptually quite simple.
The definition of L'Hopital's Rule is:
(where f(x) & g(x) are continuous, differentiable functions and f'(x) is the derivative of f(x) and g'(x) is the derivative of g(x))
If Lim[sub]x->a[/sub](f(x) / g(x)) = 0 / 0 || inf / inf then
Lim[sub]x->a[/sub](f(x) / g(x)) = Lim[sub]x->a[/sub](f'(x) / g'(x))
We can use this rule to prove how one function grows greater than another and thereby how one infinity is greater than another. Consider the example:
If f(x) = e[sup]x[/sup] and g(x) = x
Lim[sub]x->inf[/sub](e[sup]x[/sup] / x) = e[sup]inf[/sup] / inf = inf / inf (therefore L'Hopital's Rule applies, thus we derive the top and bottom and find the limit)
Lim[sub]x->inf[/sub](e[sup]x[/sup] / 1) = e[sup]inf[/sup] / 1 = e[sup]inf[/sup] = inf
The answer of infinity tells us that f(x) = e[sup]x[/sup] grows faster than g(x) = x, which can be seen quite obviously by graphing both equations. But if we simply plug in infinity to both equations we get:
f(inf) = e[sup]inf[/sup] = inf
AND g(inf) = inf
By this logic f(inf) = g(inf), but as L'Hopital's Rule proves, f(x) grows faster than g(x) and (after checking initial values) there is no point x on the interval (-inf, inf) in which g(x) >= f(x). Therefore f(x) != g(x) on any x.
As such infinity does not equal infinity.
Infinity can equal infinity, but it must be the same infinity. The infinity that is the result of f(x) is greater than the infinity created by g(x). Although f(inf) does equal infinity, it is a different infinity than the one in g(inf).
By the way there is a small error in there, I'm curious if anyone can find it and call me out on it. I'm at a loss of how to explain it without that error, but lets see if anyone finds it to begin with.
EDIT: To go back to the original example he is saying (1 - 1) * inf = inf - inf = 1 which is not true.
(1 - 1) * inf = inf - inf = 0 as it should. Think about it in a way that does not use infinities.
(1 - 1) + (1 - 1) + (1 - 1) = 0 = true
Shifting all parentheses to the right
1 + (-1 + 1) + (-1 + 1) + (-1) = 0 = still true
He is forgetting that last -1, the fact that it is (1 - 1) * inf, means that EVEN TO INFINITY, there are the same number of 1's as -1's and therefore equals 0.