A couple of problems from old contests
I found some problems from old contests in my book and I need some help solving them since I could not find the solutions online.
Some USA contest problems:
1.(1977.)Let a and b be 2 solutions of
.Prove that
is the solution of 
2.(1983.).Prove that the solutions of
are real if
German contest
3.(1977.)How many pairs of numbers p,and q from
which are smaller than 100 and for which
has a rational solution exist?
Moscow olympiad
4.(1951.) Dividing the polynomial
with
we get a quotient and remainder.What is the coefficient next to
in the quotient?
5.(1955.)If
is the root of the polynomial
and p and q don't have common divisors.If f(x) has integer coefficients then prove that
is a divisor of f(k) for every integer k.
6.(1973.) The polynomial P(x) with integer coefficients has the values 1,2,3 for some integer values of x.Prove that there is at most 1 integer x for which the polynomial has the value of 5.
Thank you very much!!!!