# Problems with LaPlace transform when 'a' is negative in e^-at

```
var('s t')
f = t^(-1)*exp(-t)-t^(-1)*exp((-3)*t)
f.laplace(t,s)
```

The above transform works as expected, however, when (-3) is changed to (3), I get the following error:

```
Traceback (click to the left of this block for traceback)
...
TypeError: ECL says: Maxima asks: Is s-3 positive, negative, or zero?
```

The Solution that I am expecting is:

```
log((s - 3)/(s + 1))
```

I don't know how to specify if s-3 is positive, negative, or zero. Any ideas?

Thanks, Taylor Killian