Truth Tables (part 3)

[@pengmingtang2811]

I'm a bit confused sir. Since in Unit 1(Evaluation of Arguments 13:00) you said that we only know an argument with false premises and a true conclusion is invalid, others' Validities are question marks. How can we know here at this video at 7:50 that without denying the antecedent then the argument must be valid?
What's more, I found another way of testing validity such as in this video ua-cam.com/video/EfsbN5YbcPQ/v-deo.html. She used the conjunction of all premise(s) to imply the conclusion to form a tautology, which shows the argument is valid. I'm wondering if this method is correct.
p.s. Thanks for the great videos you have made, they help me a lot. :)

[@vanneyaathithan9029]

My Friend, you are making too many mistakes, in your presentation.

[@ALittleBitofPhilosophy]

I certainly hope not!

[@positiveair1891]

for real? should i stop watching?

[@weisanpang7173]

Hi Dr Barry, this video is somewhat confusing, but am not saying it's having wrong content though. Given there were comments asking for clarification, i think it makes more sense that you provide justification why the video is not as erratic as the comments were claiming.

[@poormanchemist]

@@positiveair1891 Well, they haven't specified the mistakes. It could be aesthetic, minor, or even major.