The solution of the differential equation for an overdamped vibration has the form x(t) = c_1e^{r_{1}t} + c_2e^{r_{2}t}

(a) Show that x(t) is 0 at most once

(b) Show that x'(t) is 0 at most once

(c) Find the timetwhen this occurs

So x(t) = c_1e^{r_{1}t} + c_2e^{r_{2}t}

What do I do next?

and x'(t) = c_{1}r_{1}e^{r_{1}t} + c_{2}r_{2}e^{r_{2}t}