"Consider the logical arguement below involving artritrary real numbers a and b.

if a≠0 and ab = 0 then b=0.

However, b≠0. Therefore if a≠0, then ab ≠ 0.

it is given that

p: a = 0;

q: b = 0;

r: ab = 0;

translate to symbloic form and test for validity"

ans.

I have

¬p n r => q

¬q

¬p => ¬r

[[[(¬p n r ) => q] => ¬q] => ¬p] => ¬r is this setting up correct ? i just want to be sure before moving on