Question

Can someone help me with this truth table. I just don't understand how to do it.

Answer 1

An implication $(p\implies q)$ is true if either the premise $(p)$ is false, or both the premise and conclusion $(p\text{ and }q)$ are both true, and false otherwise.

$\begin{array}{c|c|c|c|c|c|c}p&q&p\implies q&\neg q&(p\implies q)\land\neg q&\neg p&(p\implies q)\land\neg q\implies\neg p\\T&T&T&&&&\\T&F&F&&&&\\F&T&T&&&&\\F&F&T&&&&\end{array}$

Negation $(\neg q)$ is straightforward; if a statement is true, then its negation is false, and vice versa.

$\begin{array}{c|c|c|c|c|c|c}p&q&p\implies q&\neg q&(p\implies q)\land\neg q&\neg p&(p\implies q)\land\neg q\implies\neg p\\T&T&T&F&&F\\T&F&F&T&&F\\F&T&T&F&&T\\F&F&T&T&&T\end{array}$

A conjunction $(p\land q)$ is true if both premises are true, and false otherwise.

$\begin{array}{c|c|c|c|c|c|c}p&q&p\implies q&\neg q&(p\implies q)\land\neg q&\neg p&(p\implies q)\land\neg q\implies\neg p\\T&T&T&F&F&F\\T&F&F&T&F&F\\F&T&T&F&F&T\\F&F&T&T&T&T\end{array}$

Finally, by the rules of implication, we can fill the last column:

$\begin{array}{c|c|c|c|c|c|c}p&q&p\implies q&\neg q&(p\implies q)\land\neg q&\neg p&(p\implies q)\land\neg q\implies\neg p\\T&T&T&F&F&F&T\\T&F&F&T&F&F&T\\F&T&T&F&F&T&T\\F&F&T&T&T&T&T\end{array}$