0

Given: $A = \{1, 2, 3, 4, 5, 6, 7\}$ and $R \subseteq A^2$, where $aRb \leftrightarrow b− a = 1$, give $R$ explicitly: $$R = ?$$

How would I got about solving this? I was thinking $R = \{[2,1],[3,2],[4,3],[5,4],[6,4],[7,6]\}$ since these are combinations result into 1.

What am I missing?

enter image description here

Caleb Stanford
  • 45,895
Jordy
  • 127

1 Answers1

2

You're almost right, but you've got your tuples backwards. "$aRb$" means "$b-a=1$," so e.g. $1R2$, not $2R1$ as you've written, etc. (Note that order matters in relations, in general.)

Noah Schweber
  • 245,398
  • Wow, I feel so stupid now, I was looking at this same thing for about an hour and couldn't find it. Thanks, I'll mark your answer as answered whenever possible! – Jordy Oct 09 '16 at 18:44
  • @Jordy Glad to help - and it happens to us all! – Noah Schweber Oct 09 '16 at 18:45