To solve the system of equations x+y=1, 
, use
solve( {x + y = 1, x^2 - y = 1}, {x,y} );
and we obtain the two sets of solutions.
Now we try a more complicated example.
We find the solution of 
which lies
in the first quadrant, and evaluate 
for this value of
, accurate to 8 digits. We start with
solve( {3*x - 2*y=2, x + y^2=7}, {x,y} );
The solution is given in terms of the roots of 
, which
is a quadratic equation, hence has two roots. So our system
has two solutions. To obtain the explicit forms of the solutions given
via "RootOf" (and to name it mysolns to refer to it later), use
mysolns := allvalues(", 'd'); use quotation mark right of semicolon key
Recall that " refers to the result of the previous computation.
(Be careful about the d - see what happens if you drop it,
or try ?allvalues). Of these solutions, we want the one for which
x,y are positive, so we approximate these solutions using
evalf( mysolns, 4 );So the first solution is the relevant one. Hence mysolns[1] is to be substituted into
. Try
mysolns[1]; subs( mysolns[1], ln(x^2+y^2) ); evalf( ", 8 );
