for what values of a does the equation:

ax^3+x^2-ax+1

have exactly two distinct real roots?

i need to find real roots for (a*x^3 + x^2  - a*x + 1) as a function of a.

and i need only the REAL roots to show in the output, no imaginaries.

thanks

program a procedure repeatedEls which takes a list and returns the sublist consisting of all elements that appeared more than once in the given list.

repeatedEls([a,b,c,d,c,d,e,f,a]);

[a,b,c]

i need to write a procedure for two sets whose final output is their intersection.

help!

okay i need to write a procedure (call it setDiff) that takes two sets and returns the set of elements in the first list that DO NOT appear in the second.

for example.

setDiff({1,2,3,4,5},{2,4,6,8});

would return

{1,3,5}

so stuck. please help!!