# Homework Help: Discrete Math

1. Jan 27, 2012

### Shackleford

Even though I'm a math major graduating in May, this is the first time I've had a formal exposure to logic.

http://i111.photobucket.com/albums/n149/camarolt4z28/Untitled-1.png

I'm not sure on e) and f).

e)

x domain: all students in this class
y domain all department courses
z domain: all departments in this school
P(x,y,z): student x taken course y in department z

$\exists x \exists z \forall y P(x,y,z)$

f)

x, y domain: students in this class
P(x,y): student x grew up in same town as student y

$\exists x \exists! y [P(x,y) ∧ (x\neq y)]$

2. Jan 27, 2012

### genericusrnme

everything looks correct to me!
is that from how to prove it a structured approach?
it looks like some questions in there..
if you haven't seen that book I'd reccomend it if you're still looking for some extra revision material

3. Jan 27, 2012

### Shackleford

I was more confident on f) than e). For some reason, e) gave me a hard time. I guess I wasn't sure about the extent to which I could use the propositional function.

Our textbook is Discrete Mathematics and Its Applications, 6th edition by Kenneth H. Rosen.