Re: A little lesson for sqrt(144) year olds.
From: Randy Poe (poespam-trap_at_yahoo.com)
Date: 07/06/04
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Date: 5 Jul 2004 22:37:33 -0700
"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?
Is -3 positive or negative?
Suppose I tell you x is positive. What sign is -x?
Suppose I tell you sqrt(x) is positive. What sign is -sqrt(x)?
If I tell you -3 is negative, does that make 3 negative?
If I tell you -sqrt(3) is negative, does that make sqrt(3) negative?
Take all the time you need.
- Randy
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