Question: probably my problem i´m gonna ask seems ridiculous and quite basic.
I want to solve an equation with the following code, where a,b,c are parameters. But surprisingly they don´t appear in the solution. I guess, it´s my mistake but I don´t see what I have done wrong. For a quite similiar equation it worked quite well and they didn´t disappear. So here is my line:

```
DSolve[Derivative[1][r][t] == a*exp (-(b - (c*1/r[t])^0.5)), r[t], t]

```

Additionally, I wanted to know if there´s a easy way to get an parametric plot.
I would be very grateful if someone could give a hint!

Cheers!

Answer: 
As per request:

```
Join@@ MapThread[Thread[#1 <-> #2] &, {{a, b}, list}] 

```

`Flatten` or `Catenate` to flatten list result from `MapThread`.

See comment by Kuba below.
How about:

```
{a, b} + list /. a_ + b_ :> a <-> b // Flatten

```