- #1

Euler2718

- 90

- 3

## Homework Statement

Determine whether the following is valid:

[tex] p \rightarrow \neg q , r \rightarrow q , r, \vdash \neg p [/tex]

## Homework Equations

Modus Ponens, disjunctive syllogism, double negation.

## The Attempt at a Solution

I've boiled it down to

[tex] p \rightarrow \neg q , q, \vdash \neg p [/tex]

However I do not understand how the book says to use disjunctive syllogism and double negation here. I've expanded the implication into its fundamental forum but I still can't see it.