Question 1201162
<br>
The statement from the professor in the first article you cite is incorrect -- or you misread the article.<br>
(NOTE: I looked at the article.  It seems poorly written and therefore confusing....)<br>
The correct rule is that {{{sqrt(xy)=(sqrt(x))(sqrt(y))}}} for all cases EXCEPT when x and y are BOTH negative.<br>
{{{sqrt((2)(2))=sqrt(4)=2}}}
{{{sqrt(2)*sqrt(2)=2}}}
the results are the same<br>
{{{sqrt((4)(-1))=sqrt(-4)=2i}}}
{{{sqrt(4)*sqrt(-1)=(2)(i)=2i}}}
the results are the same<br>
But
{{{sqrt(-1)*sqrt(-1)=(i)(i)=i^2=-1}}}
{{{sqrt((-1)(-1))=sqrt(1)=1}}}
the results are different -- because both numbers are negative<br>