1. Use cardinality to show that between any two rational numbers
there is an irrational number. Hint: Given rational numbers a <
b, first show that [a,b] is uncountable. Now use a proof by
contradiction.
2. Let X be any set. Show that X and P(X) do not have the same
cardinality. Here P(X) denote the power set of X. Hint: Use a proof
by contradiction. If a bijection:X→P(X)exists, use it to construct
a set Y ∈P(X) for which Y...
For all integers n > 2, show that the number of integer
partitions of n in which each part is greater than one is given by
p(n)-p(n-1), where p(n) is the number of integer partitions of
n.
Use cardinality to show that between any two rational numbers
there is an irrational number. Hint: Given rational numbers a <
b, first show that [a, b] is uncountable. Now use a proof by
contradiction
Partitions
Show that the number of partitions of an integer n into summands
of even size is equal to the number of partitions into summands
such that each summand occurs an even number of times.
4. Use a proof by contradiction to show that the square root of
3 is irrational. You may use the following fact: For any integer k,
if k2 is a multiple of 3, then k is a multiple of 3. Hint: The
proof is very similar to the proof that √2 is irrational.
5. Use a direct proof to show that the product of a rational
number and an integer must be a rational number.
6. Use a proof by...
For any nonnegative integer n, let Y1 < Y2 < · · · <
Y2n+1 be the ordered statistics of 2n + 1
independent observations from the uniform distribution on [−2,
2].
(i) Find the p.d.f. for Y1 and the Y2n+1.
(ii) Calculate E(Yn+1). Use your intuition to justify your
answer.
Consider an n×n square board, where n is a fixed even positive
integer. The board is divided into n 2 unit squares. We say that
two different squares on the board are adjacent if they have a
common side. N unit squares on the board are marked in such a way
that every unmarked square on the board is adjacent to at least one
marked square. Determine the smallest possible value of N.