problem getting all root solutions in maxima

Hello, don't know if I'm sending to the right email, anyway here's my
problem. I'm trying to get all the zeros of a function in a certain
interval. What I did was:
 find_root(df(x), x, a, b);
df(x) is my function, a and b the intervals.
What i get is the x of one of the zeros, but there's more than 1 zero on
that interval, but I'm not seeing how do i get all the x's corresponding to
all the zeros.
I think there's some sort of trick where you put a variable in the command,
and by changing the value(0,1,2,3...) you get all the zeros, but I'm not
seeing how to do here.

thanks for your time