First of all, it is preferable to copy and paste the input and output of Maple directly in the post.  To do so, for example, if you have this in your worksheet, highlight the input and output then copy it and paste it in here.  Al you have to do after that is to erase the second line:

> eq1 := x^2+y(x)^2 = 1;
print(`output redirected...`); # input placeholder
                                     2    2   
                             eq1 := x  + y(x)  = 1
 

to respect the format, higlight again and chose the format from normal to formatted.  This is what you will have.

> eq1 := x^2+y(x)^2 = 1;

                                     2      2    
                             eq1 := x  + y(x)  = 1

This way, it is more easier to copy and paste for us to help you.

Concerning your problem,  Maple cannot plot if you define the dependant variable represent this way:, you have to do:

> eq2 := subs(y(x) = y, eq1);

                                     2    2    
                             eq2 := x  + y  = 1

Then you can use implicitdiff

> deq1 := implicitdiff(eq2, y, x);

                                           x
                                 deq1 := - -
                                           y

and now, you are ready to plot with implicitplot from the plots packages:

>with(plots)

> implicitplot(deq1=2, x = -2 .. 2, y = -2 .. 2);

Hope it help!

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