IN:  nsolve(1/(2 - x/(1 - x)) = 1/2, x, 0)

ERROR: sec function is not in shareware and student version. Have you registered ?
OUT: x = 0
IN:  nsolve((x + 9)^(1/3) - (x - 9)^(1/3) = 3, x)
OUT: x = -13598.89921
IN:  nsolve(x^4 - 5 x^2 + 4 = 0, x)
OUT: x = 0.99999473845
IN:  nsolve(1/(x + 1) = x - 1, x)
OUT: x = 1.4142135289
