Systems of Equations
--------------------

The `a R' command can also solve systems of equations.  In this case,
the equation should instead be a vector of equations, the guess should
instead be a vector of numbers (intervals are not supported), and the
variable should be a vector of variables.  You can omit the brackets
while entering the list of variables.  Each equation must be
differentiable by each variable for this mode to work.  The result
will be a vector of two vectors: The variable values that solved the
system of equations, and the differences between the sides of the
equations with those variable values.  There must be the same number
of equations as variables.  Since only plain numbers are allowed as
guesses, the Hyperbolic flag has no effect when solving a system of
equations.

It is also possible to minimize over many variables with `a N' (or
maximize with `a X').  Once again the variable name should be replaced
by a vector of variables, and the initial guess should be an
equal-sized vector of initial guesses.  But, unlike the case of
multidimensional `a R', the formula being minimized should still be a
single formula, *not* a vector.  Beware that multidimensional
minimization is currently *very* slow.