From c23186d156c82fea356eff267d731415d135f93c Mon Sep 17 00:00:00 2001 From: Pepsi Date: Wed, 28 Jun 2023 21:35:11 +1000 Subject: [PATCH] add q3 part 1 --- q3/part1.md | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) create mode 100644 q3/part1.md diff --git a/q3/part1.md b/q3/part1.md new file mode 100644 index 0000000..194dbe4 --- /dev/null +++ b/q3/part1.md @@ -0,0 +1,19 @@ +## Question 3 + +### Part 1 + +Let d be an integer. The three requirements for d are that + +d|n+5 &(1) \\d|n^2+2 &(2) \\d|27&(3), + +Where n is any integer. + + Assume that (1) and (2) are true. The consequence of this is that there must be 2 integers, (let them be a and b), such that + +n+5&=ad &(3)\text{, derived from }(1)\\n^{2}+2&=bd &(4)\text{, derived from }(2). + +Equation (3) can be rearranged such that n=ad-5. Substituting this into (4), + +\begin{aligned}bd&=(ad+5)^{2}+2\\&=a^{2}d^{2}-10ad+25+2\\27&=bd-a^{2}d^{2}+10ad \\27&=d\left(b-a^{2}d+10a\right). &(5)\end{aligned} + +Since a,b, and d are all defined as integers, the right hand side of (5) is an integer which is divisible by d. Therefore, 27 must also be divisible by d, satisfying (3). As such, we can conclude that for all integers n, if d is an integer such that d|n+5 and d|n^2+2, then d|27. \ No newline at end of file