(10 pts.) Prove the following: If n is an odd integer then n2 is an odd integer. (This is #4, pg. 8, week 3 of the notes.)
- (10 pts.) Prove the following: If n is an odd integer then n2 is an odd integer. (This is #4, pg. 8, week 3 of the notes.)
- (10 pts.)
Assume that n is a positive integer. Use the proof by contradiction method to prove and explain:
If 3n + 2 is an even integer then n is an even integer. (This is #3, pg. 11, week 3 of the notes.)
- (15 pts.) Let A = {1,3,5,7} and B = {2,7}, with the universal set
U = {1,2,3,4,5,6,7,8,9}. Compute
- A – B
- A2 (this is the cross product)
- A B
- A (B – A)
8. (10 pts.) A bit string is a string of bits (0’s and 1’s). The length of a bit string is the number of bits in the string. An example, of a bit string of length four is 0010. An example, of a bit string of length five is 11010. Use the Rule of Products to determine the following:
(a) How many bit strings are there of length six? Explain
(b) How many bit strings are there of length six which begin with a 1 and end with a 0? Explain
(c) How many bit strings are there of length eight with even parity (an even number of 1’s)? Explain
For your information question 8 part a could have been stated the following way. Computers use bit strings of length 8, called bytes, to represent the characters (letters both upper case and lower case, punctuation symbols, [, {, the integers 0 through 9 etc) on a key board. The Extended ASCII code is one such coding system. Some examples of this code are: “a” is represented by 01100001, “A” is represented by 01000001 and “{“ is represented by 01111011 and the number 1 is represented by 00000001. How may such symbols can be described using a byte?
- (10 points) “If a < 5and b < 8 then a + b < 13”
- Write the
converse of this statement. Is the converse
true? Explain.
- Write the contrapositive of this statement. Is the contrapositive true? Explain.
- (10 points ) Express
the following in English and then determine if each statement is true: Explain
fully.
- $xÎZ (x2 = 9).
- “ yÎR (y 1)
(c) “xÎR $yÎR x + y = 3.
Extra Credit Problems. Do all, none or any one of the following extra credit problems:
1. Text page 16 number 46. Explain
2. How many bit strings of length n are palindromes? Hint: Consider two cases n is even and n is odd. Note a palindrome is a “string” of letters or numbers which read the same “frontwards” and backwards”. Examples: MOM, 1101011, 10111101 are palindromes.
3. Express the following in English and determine whether it is true. Explain. $yÎR “xÎR x + y = 5. (Warning, see example 4 pg 59)