Re: A little lesson for sqrt(144) year olds.
From: Androcles (androc1es_at_nospamblueyonder.co.uk)
Date: 07/06/04
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Date: Tue, 06 Jul 2004 16:35:47 GMT
"Randy Poe" <poespam-trap@yahoo.com> wrote in message
news:df76407e.0407052137.5f8d2992@posting.google.com...
| "Androcles" <androc1es@nospamblueyonder.co.uk> wrote in message
news:<x5jGc.331$rk4.5112897@news-text.cableinet.net>...
| > "The Ghost In The Machine" <ewill@aurigae.athghost7038suus.net> wrote in
| > message news:rmjor1-8ip.ln1@lexi2.athghost7038suus.net...
|
| > | Carefully taking square roots, one gets:
| > |
| > | x + b/(2a) = +/- sqrt(b^2 - 4ac) / (2a)
| > |
| > | and the formula follows.
| >
| > Goodness me! I'm told sqrt is always positive by Dinky the Deranged.
| > Where did the minus sign in front of it come from?
|
| The minus sign is the thing you put in front of a positive
| value to get a negative value.
|
| Thus, x+ b/(2a) can be either sqrt(b^2 - 4ac) / (2a) or its
| additive inverse, -sqrt(b^2 - 4ac) / (2a). In both cases,
| the sqrt represents a negative quantity. That's why putting
| a minus sign in front of it represents a negative quantity.
|
| Quiz for you: Is 3 positive or negative?
It is positive. Is x positive or negative?
| Is -3 positive or negative?
It is negative. Is b positive or negative?
| Suppose I tell you x is positive.
What sign is -x?
Negative.
| Suppose I tell you sqrt(x) is positive. What sign is -sqrt(x)?
Suppose I tell you sqrt(x) is negative. What sign is -sqrt(x)?
|
| If I tell you -3 is negative, does that make 3 negative?
No.
If I tell you -x is positive, does that make x negative?
| If I tell you -sqrt(3) is negative, does that make sqrt(3) negative?
No.
| If I tell you sqrt(3) is negative, does that make -sqrt(3) positive?
|
| Take all the time you need.
|
| - Randy
Take all the time you need.
Androcles
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