
 a)  You want to solve this nonlinear system of equations :
     ----------------------------------------------------

            a X*Y + b X*Z + c Z**(1/2) = d 
            e X*Y + f X*Z + g Z**(1/2) = h 
            i X*Y + j X*Z + k Z**(1/2) = l

  If you write :
                    X*Y        = x
                    X*Z        = y
                      Z**(1/2) = z
    
  You can rewrite the system :

        a x + b y + c z = d
        e x + f y + g z = h
        i x + j y + k z = l

 Which is a linear system of equation in x, y, z.

 