Question 72251
<pre><font size = 6><b>find the principal root 
 __
<font face = "symbol">Ö</font>m²

The principle square root, always 
indicated by the radical <font face = "symbol">Ö</font>
is NEVER negative.  If it were 
known that m does not represent 
a negative number then the answer 
would be just m.  However we DO 
NOT know than m is not a negative 
number, so to make sure that we 
don't answer with a negative number,
we answer
 __
<font face = "symbol">Ö</font>m² = |m|

The absolute value bars prevent the 
answer from being negative in case m 
hapens to represent a negative number.

Edwin</pre>