A math puzzle - Page 2

SmoothieX · November 20 2012, 07:31 PM

I think the problem is going from line 3 to line 4.

Line 3 is saying that -1^2 and 1^2 are both equal to 1. Which is true.

Line 4 is telling you 1 = -1. Someone conveniently forgot order of operations (PEMDAS) here.

MacLeod · November 20 2012, 08:03 PM

BODMAS on this side of the pond.

Lindley · November 20 2012, 08:21 PM

They are assuming that x^2=y^2 implies x=y, which is false.

SmoothieX · November 20 2012, 08:26 PM

I have the same math opinion as the two previous posters. 18 years later, I finally got something out of freshman HS algebra.

Asbo Zaprudder · November 20 2012, 09:50 PM

Rhubarbodendron wrote:

yep, that's what I pointed out in my last post, only less elaborate. It's quite difficult to explain mathematics in a foreign language. There are so many special terms you never learned at school.

Totally off-topic, but I just have to ask: what kind of spider is the one in your avatar, Asbo Zaprudder? It's pretty!

A jumping spider - family Salticidae - although I'm not sure which one of the approx 5000 species.

Alidar Jarok · November 21 2012, 05:40 AM

Others have explained it, but if you write out the squares for (3 - 4) and (5 - 4) it becomes obvious:

(3 - 4)^2 becomes (3 - 4) (3 - 4)

So it would be:
(3 - 4) (3 - 4) = (5 - 4) (5 - 4)
There's no way for that to turn into
3 - 4 = 5 - 4

M'Sharak · November 21 2012, 09:19 AM

Asbo Zaprudder wrote:

Rhubarbodendron wrote:

...

Totally off-topic, but I just have to ask: what kind of spider is the one in your avatar, Asbo Zaprudder? It's pretty!

A jumping spider - family Salticidae - although I'm not sure which one of the approx 5000 species.

I think it's this kind, especially if the ID which goes with the source image is anything to go by.

Asbo Zaprudder · November 21 2012, 09:21 AM

These puzzles usually boil down to division by zero or multiplication by zero in one of the steps. I hadn't seen this variant before.

ETA: Thanks, M'Sharak.

Rhubarbodendron · November 21 2012, 05:10 PM

me neither. A very nice variation of the old math trick

I had suspected it to be a Salticidae - the eye position is typical. In my country we only have very small black and white striped ones (Salticus scenicus) and even tinier brown ones with 4 dots (Sitticus pubescens). Both species have black eyes with blue reflections. The green reflection in your avatar-spider's eyes is quite attractive

JarodRussell · November 21 2012, 08:55 PM

3-4 is not equal to 5-4, and one can also completly above any line before that.

November 20 2012, 07:31 PM	#16
SmoothieX Vice Admiral Location: Massachusetts	Re: A math puzzle I think the problem is going from line 3 to line 4. Line 3 is saying that -1^2 and 1^2 are both equal to 1. Which is true. Line 4 is telling you 1 = -1. Someone conveniently forgot order of operations (PEMDAS) here. Last edited by SmoothieX; November 20 2012 at 08:27 PM.

November 20 2012, 08:03 PM	#17
MacLeod Vice Admiral Location: Great Britain	Re: A math puzzle BODMAS on this side of the pond. __________________ On the continent of wild endeavour in the mountains of solace and solitude there stood the citadel of the time lords, the oldest and most mighty race in the universe looking down on the galaxies below sworn never to interfere only to watch.

November 20 2012, 08:21 PM	#18
Lindley Moderator with a Soul Location: Fairfax, VA	Re: A math puzzle They are assuming that x^2=y^2 implies x=y, which is false. __________________ Lead Organizer for EVN: Firefly. "So apparently the really smart zombies have automatic weapons!" -Torg, Sluggy Freelance

November 20 2012, 08:26 PM	#19
SmoothieX Vice Admiral Location: Massachusetts	Re: A math puzzle I have the same math opinion as the two previous posters. 18 years later, I finally got something out of freshman HS algebra.

November 21 2012, 05:40 AM	#21
Alidar Jarok Everything in moderation but moderation Location: Arlington, VA	Re: A math puzzle Others have explained it, but if you write out the squares for (3 - 4) and (5 - 4) it becomes obvious: (3 - 4)^2 becomes (3 - 4) (3 - 4) So it would be: (3 - 4) (3 - 4) = (5 - 4) (5 - 4) There's no way for that to turn into 3 - 4 = 5 - 4 __________________ When on Romulus, Do as the Romulans

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November 21 2012, 09:21 AM	#23
Asbo Zaprudder Rear Admiral Location: Chairman of the bored	Re: A math puzzle These puzzles usually boil down to division by zero or multiplication by zero in one of the steps. I hadn't seen this variant before. ETA: Thanks, M'Sharak. __________________ "It is a lonely life, the way of the necromancer... oh, yes. Lacrimae Mundi - the tears of the world."

November 21 2012, 05:10 PM	#24
Rhubarbodendron Fleet Captain Location: Milky Way, outer spiral arm, Sol 3	Re: A math puzzle me neither. A very nice variation of the old math trick I had suspected it to be a Salticidae - the eye position is typical. In my country we only have very small black and white striped ones (Salticus scenicus) and even tinier brown ones with 4 dots (Sitticus pubescens). Both species have black eyes with blue reflections. The green reflection in your avatar-spider's eyes is quite attractive __________________ Eve is the revised, improved and updated version of Adam [Helen Vita]

November 21 2012, 08:55 PM	#25
JarodRussell Vice Admiral	Re: A math puzzle 3-4 is not equal to 5-4, and one can also completly above any line before that. __________________ lol l /\