Why is 'x' the unknown? | Terry Moore

714,315 views ใƒป 2012-06-06

TED


ืื ื ืœื—ืฅ ืคืขืžื™ื™ื ืขืœ ื”ื›ืชื•ื‘ื™ื•ืช ื‘ืื ื’ืœื™ืช ืœืžื˜ื” ื›ื“ื™ ืœื”ืคืขื™ืœ ืืช ื”ืกืจื˜ื•ืŸ.

00:00
Translator: Timothy Covell Reviewer: Jenny Zurawell
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ืžืชืจื’ื: Orr Schlesinger ืžื‘ืงืจ: Ido Dekkers
00:15
I have the answer to a question that we've all asked.
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ืžืฆืืชื™ ืืช ื”ืชืฉื•ื‘ื” ืœืฉืืœื” ืฉื›ื•ืœื ื• ืฉื•ืืœื™ื.
00:19
The question is,
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ื”ืฉืืœื” ื”ื™ื,
00:20
Why is it that the letter X
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ืœืžื” ื“ื•ื•ืงื ื”ืื•ืช "X"
00:22
represents the unknown?
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ืžื™ื™ืฆื’ืช ืืช ื”ื ืขืœื?
00:24
Now I know we learned that in math class,
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ืื ื™ ื™ื•ื“ืข ืฉืœืžื“ื ื• ืืช ื–ื” ื‘ืฉื™ืขื•ืจื™ ืžืชืžื˜ื™ืงื”,
00:27
but now it's everywhere in the culture --
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ืื‘ืœ ืขื›ืฉื™ื• ื–ื” ื ืžืฆื ื‘ื›ืœ ืžืงื•ื ื‘ืชืจื‘ื•ืช --
00:29
The X prize, the X-Files,
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"ืคืจืก X", "ืชื™ืงื™ X"
00:32
Project X, TEDx.
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"ืคืจื•ื™ื™ืงื˜ X", TEDx.
00:36
Where'd that come from?
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ืžืื™ืคื” ื–ื” ืžื’ื™ืข?
00:38
About six years ago
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ืœืคื ื™ ื‘ืขืจืš ืฉืฉ ืฉื ื™ื
00:39
I decided that I would learn Arabic,
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ื”ื—ืœื˜ืชื™ ืœืœืžื•ื“ ืขืจื‘ื™ืช,
00:42
which turns out to be a supremely logical language.
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ืฉื”ืชื’ืœืชื” ื›ืฉืคื” ืžืื•ื“ ืœื•ื’ื™ืช ื•ื”ื’ื™ื•ื ื™ืช.
00:46
To write a word or a phrase
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ืœื›ืชื•ื‘ ืžื™ืœื”, ื‘ื™ื˜ื•ื™
00:48
or a sentence in Arabic
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ืื• ืžืฉืคื˜ ื‘ืขืจื‘ื™ืช
00:50
is like crafting an equation,
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ื–ื” ื›ืžื• ืœื‘ื ื•ืช ืžืฉื•ื•ืื”,
00:52
because every part is extremely precise
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ื›ื™ื•ื•ืŸ ืฉื›ืœ ื—ืœืง ื”ื•ื ืžืื•ื“ ืžื“ื•ื™ื™ืง
00:54
and carries a lot of information.
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ื•ื ื•ืฉื ื›ืžื•ื™ื•ืช ื’ื“ื•ืœื•ืช ืฉืœ ืžื™ื“ืข.
00:57
That's one of the reasons
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ื–ื• ืื—ืช ื”ืกื™ื‘ื•ืช
00:58
so much of what we've come to think of
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ืฉื”ืจื‘ื” ืžืžื” ืฉืื ื• ืžื—ืฉื™ื‘ื™ื
01:00
as Western science and mathematics and engineering
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ื›ืžื“ืข, ืžืชื™ืžื˜ื™ืงื” ื•ื”ื ื“ืกื” ืžืขืจื‘ื™ื™ื
01:04
was really worked out in the first few centuries of the Common Era
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ื‘ืขืฆื ืคื•ืชื—ื• ื‘ืžืื•ืช ื”ืจืืฉื•ื ื•ืช ืœืกืคื™ืจื”
01:07
by the Persians and the Arabs and the Turks.
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ืขืœ ื™ื“ื™ ื”ืคืจืกื™ื ื”ืขืจื‘ื™ื ื•ื”ื˜ื•ืจืงื™ื.
01:10
This includes the little system in Arabic
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ื–ื” ื›ื•ืœืœ ื’ื ืžืขืจื›ืช ืงื˜ื ื” ื‘ืขืจื‘ื™ืช
01:13
called al-jebra.
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ืฉื ืงืจืืช ืืœ-ื’'ื‘ืจื”.
01:14
And al-jebr roughly translates to
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ืืœ-ื’'ื‘ืจ ืžืชื•ืจื’ื ื‘ืฆื•ืจื” ื’ืกื”
01:18
"the system for reconciling disparate parts."
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ืœ "ื”ืžืขืจื›ืช ืœื™ื™ืฉื•ื‘ ื—ืœืงื™ื ืฉื•ื ื™ื"
01:21
Al-jebr finally came into English as algebra.
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ื‘ืกื•ืคื• ืฉืœ ื“ื‘ืจ ืืœ-ื’'ื‘ืจ ื”ืคืš ื‘ืื ื’ืœื™ืช ืœืืœื’ื‘ืจื”.
01:25
One example among many.
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ื–ื• ื“ื•ื’ืžื ืื—ืช ืžืชื•ืš ืจื‘ื•ืช.
01:28
The Arabic texts containing this mathematical wisdom
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ื”ื˜ืงืกื˜ื™ื ื”ืขืจื‘ื™ื™ื ื”ืžื›ื™ืœื™ื ืืช ื”ื™ื“ืข ืฉืœ ื”ืžืชืžื˜ื™ืงื”
01:32
finally made their way to Europe --
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ืžืฆืื• ืืช ื“ืจื›ื ื‘ืกื•ืคื• ืฉืœ ื“ื‘ืจ ืœืื™ืจื•ืคื” --
01:33
which is to say Spain --
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ืœื™ืชืจ ื“ื™ื•ืง ืœืกืคืจื“ --
01:35
in the 11th and 12th centuries.
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ื‘ืžืื•ืช ื”-11 ื•ื”-12 ืœืกืคื™ืจื”.
01:37
And when they arrived
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ื•ื›ืืฉืจ ื”ื ื”ื’ื™ืขื•
01:38
there was tremendous interest
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ื”ื™ื” ืขื ื™ื™ืŸ ื’ื“ื•ืœ ืžืื•ื“
01:40
in translating this wisdom
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ืœืชืจื’ื ืืช ื”ื˜ืงืกื˜ื™ื ื”ืœืœื•
01:42
into a European language.
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ืœืฉืคื” ืื™ืจื•ืคืื™ืช.
01:43
But there were problems.
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ืื‘ืœ ื”ื™ื• ื‘ืขื™ื•ืช.
01:46
One problem
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ืื—ืช ืžื”ื‘ืขื™ื•ืช ื”ื™ืชื”
01:47
is there are some sounds in Arabic
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ืฉืืช ื—ืœืง ืžื”ืฆืœื™ืœื™ื ื‘ืฉืคื” ื”ืขืจื‘ื™ืช
01:50
that just don't make it through a European voice box
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ืœื ื”ื™ื” ืœืื™ืจื•ืคืื™ื ืงืœ ืœื‘ื˜ื
01:53
without lots of practice.
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ืœืœื ืชืจื’ื•ืœ ืจื‘.
01:55
Trust me on that one.
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ืชืืžื™ื ื• ืœื™ ื‘ืงื˜ืข ื”ื–ื”.
01:57
Also, those very sounds
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ื‘ื ื•ืกืฃ, ื”ืฆืœื™ืœื™ื ื”ืœืœื•
01:59
tend not to be represented
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ื ื•ื˜ื™ื ืœื ืœื”ื™ื•ืช ืžื™ื•ืฆื’ื™ื
02:01
by the characters that are available in European languages.
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ืขืœ ื™ื“ื™ ื”ืื•ืชื™ื•ืช ื”ืงื™ื™ืžื•ืช ื‘ืฉืคื•ืช ื”ืื™ืจื•ืคืื™ื•ืช.
02:05
Here's one of the culprits.
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ื”ื ื” ืื—ื“ ืžื”ืืฉืžื™ื.
02:06
This is the letter sheen,
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ื–ื• ื”ืื•ืช ืฉื™ืŸ (ื‘ืขืจื‘ื™ืช),
02:08
and it makes the sound we think of as SH -- "sh."
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ื•ื”ื™ื ื™ื•ืฆืจืช ืืช ื”ืฆืœื™ืœ ื”ืžื™ื•ืฆื’ ื‘ืื ื’ืœื™ืช ืขืœ ื™ื“ื™ ืฆื™ืจื•ืฃ ื”ืื•ืชื™ื•ืช SH.
02:12
It's also the very first letter
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ื–ื• ื’ื ื”ืื•ืช ื”ืจืืฉื•ื ื”
02:14
of the word shayun,
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ืฉืœ ื”ืžื™ืœื” "ืฉืืœืืŸ",
02:17
which means "something"
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ืฉืคื™ืจื•ืฉื” ื”ื•ื "ืžืฉื”ื•"
02:19
just like the the English word "something" --
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ื‘ื“ื™ื•ืง ื›ืžื• ื”ืžื™ืœื” ื‘ืื ื’ืœื™ืช "something" --
02:21
some undefined, unknown thing.
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ืžืฉื”ื• ืœื ืžื•ื’ื“ืจ, ืœื ื™ื“ื•ืข.
02:24
Now in Arabic,
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ื•ื‘ืขืจื‘ื™ืช,
02:25
we can make this definite
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ืื ื—ื ื• ื™ื›ื•ืœื™ื ืœื”ืคื•ืš ืžืฉื”ื• ืœื™ื“ื•ืข
02:26
by adding the definite article "al."
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ืขืœ ื™ื“ื™ ื”ื•ืกืคืช "ืืœ" (ื”' ื”ื™ื“ื™ืขื”).
02:28
So this is al-shayun --
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ืื– ื–ื” ื”ื•ื - ืืœ-ืฉืืœืืŸ --
02:31
the unknown thing.
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ื”ื“ื‘ืจ ื”ืœื ื™ื“ื•ืข.
02:33
And this is a word that appears throughout early mathematics,
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ื–ื• ืžื™ืœื” ืฉืžื•ืคื™ืขื” ืจื‘ื•ืช ื‘ืจื—ื‘ื™ ื”ื˜ืงืกื˜ื™ื ื”ืžืชืžื˜ื™ื™ื ื”ืจืืฉื•ื ื™ื,
02:36
such as this 10th-century derivation of roots.
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ื›ืžื• ื”ื˜ืงืกื˜ ื”ื–ื” ืžื”ืžืื” ื”ืขืฉื™ืจื™ืช.
02:43
The problem for the Medieval Spanish scholars
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ื”ื‘ืขื™ื” ืฉืขืžื“ื” ื‘ืคื ื™ ื”ื—ื›ืžื™ื ื”ืกืคืจื“ื™ื ื‘ื™ืžื™ ื”ื‘ื™ื ื™ื™ื
02:46
who were tasked with translating this material
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ืฉื ื“ืจืฉื• ืœืชืจื’ื ืืช ื”ื—ื•ืžืจื™ื ื”ืœืœื•
02:48
is that the letter sheen and the word shayun
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ื”ื™ืชื” ืฉื”ืื•ืช "ืฉื™ืŸ" ื•ื”ืžื™ืœื” "ืฉืืœืืŸ"
02:53
can't be rendered into Spanish
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ืœื ื™ื›ื•ืœื•ืช ืœื”ื™ื•ืช ืžืชื•ืจื’ืžื•ืช ื™ืฉื™ืจื•ืช ืœืกืคืจื“ื™ืช
02:55
because Spanish doesn't have that SH,
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ื›ื™ื•ื•ืŸ ืฉื‘ืกืคืจื“ื™ืช ืœื ืงื™ื™ื ืฆื™ืจื•ืฃ ื”ืื•ืชื™ื•ืช SH,
02:57
that "sh" sound.
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ืฉื™ื•ืฆืจ ืืช ื”ืฆืœื™ืœ ืฉืœ ื”ืื•ืช ืฉื™ืŸ (SH).
02:59
So by convention,
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ืื– ื ื•ืฆืจื” ืื™ื–ืฉื”ื™ื ื”ืกื›ืžื”,
03:00
they created a rule in which
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ืฉื”ื ื™ืฆืจื• ื›ืœืœ ืฉื‘ื•
03:02
they borrowed the CK sound, "ck" sound,
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ื”ื ืœืงื—ื• ืืช ื”ืฆืœื™ืœ "ืกืง" (CK),
03:06
from the classical Greek
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ืžื”ื™ื•ื•ื ื™ืช ื”ืงืœืืกื™ืช
03:08
in the form of the letter Kai.
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ื‘ืฆื•ืจืช ื”ืื•ืช "ืงืื™".
03:10
Later when this material was translated
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ืžืื•ื—ืจ ื™ื•ืชืจ, ื›ืืฉืจ ื”ื—ื•ืžืจ ืชื•ืจื’ื
03:13
into a common European language,
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ืœืฉืคื” ืื™ืจื•ืคืื™ืช ื ืคื•ืฆื”,
03:15
which is to say Latin,
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ื”ืœื˜ื™ื ื™ืช,
03:18
they simply replaced the Greek Kai
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ื”ื ืคืฉื•ื˜ ื”ื—ืœื™ืคื• ืืช ื”ืื•ืช "ืงืื™"
03:20
with the Latin X.
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ืขื ื”ืื•ืช ื”ืœื˜ื™ื ื™ืช "X".
03:22
And once that happened,
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ื•ื‘ืจื’ืข ืฉื–ื” ืงืจื”,
03:23
once this material was in Latin,
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ื‘ืจื’ืข ืฉื”ื˜ืงืกื˜ื™ื ื”ื™ื• ื‘ืœื˜ื™ื ื™ืช,
03:26
it formed the basis for mathematics textbooks
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ื”ื ื”ื™ื•ื• ืืช ื”ื‘ืกื™ืก ืœืกืคืจื™ ื”ืžืชืžื˜ื™ืงื”
03:29
for almost 600 years.
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ื›ืžืขื˜ 600 ืฉื ื™ื ืœืื—ืจ ืžื›ืŸ.
03:31
But now we have the answer to our question.
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ืขื›ืฉื™ื• ื™ืฉ ืœื ื• ืืช ื”ืชืฉื•ื‘ื” ืœืฉืืœืชื™ื ื•.
03:33
Why is it that X is the unknown?
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ืžื“ื•ืข ื”ืื•ืช "X" ืžื™ื™ืฆื’ืช ืืช ื”ื ืขืœื?
03:36
X is the unknown
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X ื”ื•ื ื”ื ืขืœื
03:38
because you can't say "sh" in Spanish.
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ื›ื™ื•ื•ืŸ ืฉืื™ ืืคืฉืจ ืœื”ื’ื™ื“ "ืฉ" (SH) ื‘ืกืคืจื“ื™ืช.
03:42
(Laughter)
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(ืฆื—ื•ืง)
03:44
And I thought that was worth sharing.
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ื•ื—ืฉื‘ืชื™ ืฉืฉื•ื•ื” ืœืฉืชืฃ ืืชื›ื ื‘ืžื™ื“ืข ื”ื–ื”.
03:46
(Applause)
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(ืžื—ื™ืื•ืช ื›ืคื™ื™ื)
ืขืœ ืืชืจ ื–ื”

ืืชืจ ื–ื” ื™ืฆื™ื’ ื‘ืคื ื™ื›ื ืกืจื˜ื•ื ื™ YouTube ื”ืžื•ืขื™ืœื™ื ืœืœื™ืžื•ื“ ืื ื’ืœื™ืช. ืชื•ื›ืœื• ืœืจืื•ืช ืฉื™ืขื•ืจื™ ืื ื’ืœื™ืช ื”ืžื•ืขื‘ืจื™ื ืขืœ ื™ื“ื™ ืžื•ืจื™ื ืžื”ืฉื•ืจื” ื”ืจืืฉื•ื ื” ืžืจื—ื‘ื™ ื”ืขื•ืœื. ืœื—ืฅ ืคืขืžื™ื™ื ืขืœ ื”ื›ืชื•ื‘ื™ื•ืช ื‘ืื ื’ืœื™ืช ื”ืžื•ืฆื’ื•ืช ื‘ื›ืœ ื“ืฃ ื•ื™ื“ืื• ื›ื“ื™ ืœื”ืคืขื™ืœ ืืช ื”ืกืจื˜ื•ืŸ ืžืฉื. ื”ื›ืชื•ื‘ื™ื•ืช ื’ื•ืœืœื•ืช ื‘ืกื ื›ืจื•ืŸ ืขื ื”ืคืขืœืช ื”ื•ื•ื™ื“ืื•. ืื ื™ืฉ ืœืš ื”ืขืจื•ืช ืื• ื‘ืงืฉื•ืช, ืื ื ืฆื•ืจ ืื™ืชื ื• ืงืฉืจ ื‘ืืžืฆืขื•ืช ื˜ื•ืคืก ื™ืฆื™ืจืช ืงืฉืจ ื–ื”.

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