You may not be doing anything wrong. I got two different kinds of errors:

```
TypeError: Error executing code in Maxima
CODE:
sage99 : ('y(x))+(diff('y(x), x, 1))+(-1)$
Maxima ERROR:
sage99 : ('y(x))+(diff('y(x), x, 1))+(-1)$
stdin:7094:Incorrect syntax: Too many )'s
(%i87)
stdin:7145:Incorrect syntax: Premature termination of input at $.
(%i88)
```

and

```
sage: desolve(diff(y,x) + y - 1, y)
sage103
```

before getting the right answer:

```
sage: desolve(diff(y,x) + y - 1, y)
(c + e^x)*e^(-x)
```

Then I did it from a restart and everything worked the first time, and I can't reproduce the errors anymore. Looks like the maxima interface can get itself into a state, whether because of something I'd done previously or not. But this definitely shouldn't happen: were these the same kinds of errors you saw?

Surprising! I copy pasted both the equations and they work fine for me.