Can someone check my answers to this sample test thing?

1. Consider the following subsets of the set N of natural numbers i) The set of prime numbers; ii) The set of even numbers; iii) The set of non-prime numbers. How many of these sets are bounded below? a) 0; b) 1; c) 2; d) 3.
2. Consider the equations m = 9987n + 3989;m = 7871n + 723. For how many integer values of n can they both be true? a) 0 b) 1 c) 2 d) 3
3. The least element of the set R = {m−3qn ∈N : q ∈N}, where m = 555 and n = 11, (a) does not exist (b) is 1 (c) is 5 (d) is 27.

I put d, a and d. am I correct? This is just a few questions from a sample test before the real thing tomorrow, but they haven't supplied answers for me to check my work.

(edited 9 years ago)

Reply 1

james22

Only 2 is right.

For 1, why do you think that none of them are bounded below? For example the primes are bounded below by 2.

For 3, what about q=1000? EDIT: Ignore this bit.

(edited 9 years ago)

Reply 2

pineapplechemist

Original post by james22

Only 2 is right.

For 1, why do you think that none of them are bounded below? For example the primes are bounded below by 2.

For 3, what about q=1000?

Could you explain what you mean by your comment about my question three please? My answer for the question about bounded sets was a mistake, I meant d)

Reply 3

ghostwalker

Original post by pineapplechemist

...

d) is corrrect for number 3.

Reply 4

james22

Original post by pineapplechemist

Could you explain what you mean by your comment about my question three please? My answer for the question about bounded sets was a mistake, I meant d)