- #1

Lilian Sa

- 18

- 2

**Summary::**solution of first order derivatives

we had in the class a first order derivative equation:

##\frac{dR(t)}{dt}=-\sqrt{\frac{2GM(R)}{R}}##

in which R dependent of time.

and I don't understand why the solution to this equation is:

##R(t)={\frac{3}{2}}^{\frac{3}{2}}{2GM}{\frac{1}{3}}{(t_*-t)}^{\frac{2}{3}}##

thanks

**[Moderator's note: moved from a technical forum.]**