veamos si esta es la ecuación
[tex]r = \frac{d}{1-dt} [/tex]
[tex]r(1-dt) = d[/tex]
[tex]1-dt = \frac{d}{r} [/tex]
[tex]dt = 1- \frac{d}{r} [/tex]
[tex]t = \frac{1- \frac{d}{r} }{d} = \frac{ \frac{r-d}{r} }{d} = \frac{r-d}{dr} [/tex]
despeje para t
[tex]r(1-dt) = d[/tex]
[tex]r-dtr = d \\ r = d + dtr \\ r = d(1 + tr) \\ d = \frac{r}{1 + tr} [/tex]
