Maths Problems for a thought

[Joel8945]

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This is probably too easy for you guys but I found it fun!

find the limit (x -> ∞) [sqrt(9x^2+x) - 3x]

[Joel8945]

Originally Posted by humphdogg

let a = b.
multiply both sides by a.
a^2 = ab
add a^2 to both sides.
2a^2 = a^2 + ab
subtract 2ab from both sides.
2a^2 - 2ab = a^2 - ab
take out a^2 - ab as a common factor.
2(a^2 - ab) = 1(a^2 - ab)
divide through by a^2 - ab.
2 = 1
subtract 1 from both sides.
1 = 0

QED.

This isn't about your maths problem, rather this PhB degree! Now I searched up PhB and its a bachelor of philosophy. Now I have heard of a PhD (something I would personally love to be able to earn, but, I'm a bit skeptical about whether I would be smart enough to get one).

With your degree what are you majoring in and after completing this degree what would you considering doing? I'm guessing a PhD.

[Joel8945]

Originally Posted by field5

Actually 0.9' does = 1

Let x = 0.9'
Therefor 10x = 9.9'
Therefor 9x= 9
Therefore x = 1

10x = 9.9'

now

9x = 8.9'
x = 8.9'/9
x = 0.9'

Your a hoot

In this proof you made the assumption that 8.9' = 9 (shame on you)

[tommykins]

Originally Posted by Joel8945

10x = 9.9'

now

9x = 8.9'
x = 8.9'/9
x = 0.9'

Your a hoot

In this proof you made the assumption that 8.9' = 9 (shame on you)

.....

[humphdogg]

Originally Posted by Joel8945

This isn't about your maths problem, rather this PhB degree! Now I searched up PhB and its a bachelor of philosophy. Now I have heard of a PhD (something I would personally love to be able to earn, but, I'm a bit skeptical about whether I would be smart enough to get one).

With your degree what are you majoring in and after completing this degree what would you considering doing? I'm guessing a PhD.

Hah, it's very much the obvious answers here. I'm majoring in pure maths (hoping to somehow combine analysis and number theory for my honours topic next year), and yeah, after I graduate I plan to do a PhD (in pure maths, of course). Not sure where though... Maybe somewhere decent in the UK or US.

[Cobalt]

Prove that infinity times zero=-1

[crashnow]

umm? u cant. u cant multiply a number by a concept, its undefined.

[Cobalt]

To tell you the truth I made that one up and here's the answer:

What happens when you multiply two gradients that are perpendicular? They equal -1. Therefore if you multiply zero gradient (horizontal line) with an infinity gradient (vertical line), you get -1 since they are perpendicular.

[tommykins]

lol @ infinity gradient

[crashnow]

how can gradient b infinite if its vertical line? gradient is rise over run. rise is infinite over zero run. anything over zero is undefined. so gradient is undefined not infinite

[Cobalt]

Anything over zero is infinity. It's another word for undefined. For example, when we talk about asymptotes, we state that the function approaches infinity or is undefined at that point. Both words are used in the same context.

[humphdogg]

Originally Posted by Cobalt

Anything over zero is infinity. It's another word for undefined. For example, when we talk about asymptotes, we state that the function approaches infinity or is undefined at that point. Both words are used in the same context.

Not quite. When you're talking about limits, for example, you can make something over zero to equal anything you want: for any positive number a, consider the limit as x tends to zero of
a sin x / x
This approaches a as x tends to zero, even though the denomenator approaches zero as x tends to zero.

[sikhman]

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