An argument is invalid if and only if all the premises is true and the conclusion is false.
We can test the invalidity of the argument by assuming all the premises are true and seeing whether it is possible for the conclusion to be false. If the conclusion is possible to be false, then, the argument is invalid.
A valid argument, on the other hand, is valid if and only if it is necessary that:
1) if all of the premises are true, then the conclusion is true
2) if all of the premises are true, then the conclusion must be true
3) it is impossible that all the premises are true and the conclusion is false.
When you preview something, you inspect it. Previewing helps you get a glimpse of what's ahead before you read or something, kind of like skimming.
For the first picture I believe it’s the Mr. Yuri Jackson one and for the second I think it might be the “I offer an alternative” not sure though.
True. They dont try to go more out of the different norms