# desolve (how can i enable numeric?)

Hi, I am sorry for asking this, but I have been looking all over the internet now and I can't find any solution to this.

When i am using `desolve`

i sometimes get some crazy outputs which is not relevant for me at all.

For instance i am trying to desolve this equation

y' = 0.00054 \cdot y \cdot (500 - y)

So i white

```
k = var('k')
x = var('x')
y = function('y')(x)
```

Then i define my `de`

```
de = diff(y,x) == 0.00054*1*y*(500-y)
```

And i desolve like i have done before with many other equations without any problem

```
desolve(de,y,[0,90])
```

But i get this result

```
-100/27*log(y(x) - 500) + 100/27*log(y(x)) == -100/27*I*pi + x - 100/27*log(410) + 100/27*log(90)
```

The right result should be:

```
y = 500/(1+4.556*e^(-0.27*x))
```

Please help me. I have been readning in the doc section about desolve and many other places, but there is so much stuff i dont understand. I am on the edge to install a subsitute CAS program to help me everytime sagemath fails.

The documentation is not as user friendly as a guide; this is useful. I don't have experience with differential equations but adding contrib_ode=True, show_method=True to desolve tells you it's separable and after adding the lines c = de.variables()[0] sol = solve(de,y) ; sol as suggested in the guide (page 219) gets you closer. One of the experts here will know what to do.

Thank you so much!! I will look in this guide now :D