non-linear solve?

hi: could someone please point me to a function that allows me to
solve general non-linear functions?

irr.in <- function(r, c1, c2, c3 ) { return(c1+c2/(1+r) +

c3/(1+r)^2); }

solve.nonlinear( irr.in, -100, 60, 70 );

  0.189

  If someone has written an irr function, this would be helpful,
  too---though not difficult to write, either. thanks for any
  pointers.

  Regards,

  /iaw