Num Error, Bad Argument Type

[Joseph Colannino]

When I try to take the cube root of 3 + 4i I get a numerical error when I hit the NUM key. Why? Also, when I take the cube root of -5 I obtain a + bi notation, but when I take the ninth root I obtain exponential notation. Why don't I get consistent notation? Finally, taking the cube root of -5 and taking it again results in "Num Error: Bad Argument Type," yet taking the ninth root of -5 results in a proper numerical evaluation.