YA query re use of assume (Have RTM)



Greetings list

I'm still getting used to this, but I've been lurking a while and 
now I have to start doing basic college first year calc. I'm 
working up to Stochastic processes later in the year.
I'll do it in Mathematica if I need to but I'd rather use your 
package, it suits me better.

I'm getting to grips with parts and equation manipulation, so I 
tryed this, prove eqn1 converges to root n for x > 0:

eqn1 : (1/2)*(x + (n/x)) = 0$ 
eqn1 : eqn1*2$
eqn1 : eqn1 - part(part(eqn1, 1), 1)$ 
eqn1 : eqn1^2$
eqn1 : eqn1 * part(part(eqn1, 1), 2)$
eqn1 : eqn1^(1/4)$
eqn1;

And I get something that can be written in c as sqrt(n) == abs(x)
Fair enough

I also got rid of the abs by doing 

assume(n > 0, x > 0);

which is fine cause my case allows it.

So having proved this 'manually' I want to try and get solve to 
do it automatically. 

But when I do this:

assume(n>0)$
eqn2 : (1/2)*(x + (n/x)) = 0$
soln : solve(eqn2, x)$
soln; 

I get [ -%i*n^(1/2), %i*n^(1/2) ]

What am I missing, if I can manipulate the expression around to 
be what I thought, then these 2 expressions should be the same, 
but they aren't what am I missing.

PS wxMaxima should support copy and paste from the interface, it 
seems broken on my Gentoo system. wxMaxima 0.7.4, Maxima 5.14.0 
all build with recent libs as at 1 March. 

TIA and sorry for a long post.
Any ideas on any of this are appreciated.

rgrieve at cs.otago.ac.nz