zeroes function returning incorrectly

[derekwiers-wk]

$ mdlt zeroes x^2 - 14x + 4
[7, 7] # wrong
$ mdlt zeroes x^2 - 14x + 3
[7, 7] # wrong
$ mdlt zeroes "x^2 - 15x - 1932847239"
[-15, 15] # wrong

Not sure what's going on here...