Answer:
(1) To prove that for any integer n, there exist two integers a and b of opposite parity such that an + b is an odd integer, we can consider two cases: if n is even, then we can choose a = 1 and b = 1, which are both odd, and their sum will be even. Then, we can add another odd number, such as 1, to the sum to make it odd. Therefore, we have an + b = n + 2, which is odd. If n is odd, then we can choose a = 1 and b = −1, which are of opposite parity, and their sum will also be odd. Then, we can add (n + 1) to the sum to make it equal to an + b = n + 1. Therefore, we have proven the statement for both even and odd n.
(2) To prove the contrapositive of the statement "If p is a prime greater than or equal to 5, then either 3 | (p+2) or 3 | (p-2)", we assume that p is a prime greater than or equal to 5 and that 3 does not divide (p+2) or (p-2). Since p is odd, it can be written as p = 3k + 1 or p = 3k + 2 for some integer k. If p = 3k + 1, then p+2 = 3k + 3 = 3(k+1), which is divisible by 3. This contradicts our assumption that 3 does not divide (p+2). Similarly, if p = 3k + 2, then p-2 = 3k, which is divisible by 3, again contradicting our assumption. Therefore, we have proven the contrapositive, which implies the original statement.
(3) To prove by contradiction that log3045 is irrational, we assume that log3045 is a rational number and can be expressed as a ratio of two integers, say log3045 = p/q, where p and q are coprime integers. Then, we can exponentiate both sides of this equation to get 45 = 3^(p/q). Taking the qth power of both sides, we get 45^q = 3^p. Since 3 and 45 are coprime, this implies that both q and p must be multiples of each other
Explanation: