problems

Please look at the following problems

Problem 1
assume(a>b); 

 conjugate(sqrt(a-b));

Maxima displays the correct result:  
 
sqrt(a-b)   

however, for:  
 
assume(b>a); 

the calculation of  
 
conjugate( sqrt(a-b))

becomes too difficult. 
One would expect the result:

      -%i*sqrt(b-a)                                  )
 
 
Problem 2
An attempt of calculation the laplacian of 1/r, where
 
     r:=sqrt(x^2+y^2+z^2)
       laplacian(1/r)
gives a wrong result: "zero" .
Is it possible to evaluate a correct result, using Maxima ? 
 
Problem 3. 

How, using Maxima, to solve in elegant way a system of inequalties, like: 

                (x^2+x+1)^x>0 and x>-2 

Thanks in advance
Leon