Integrate Countersign Proof with airSlate SignNow

Integrate countersign proof

welcome back to another video and for this video I will be looking at methods of proof using logic theory and we're looking at counter example direct method contrapositive and contradiction and the first one will be looking at this counter example so this method is useful in disproving statements of the form for all X such that P of X or proof there exists an X such that P of X so here we have an example for all positive into n if n is prime then n plus 1 n plus 2 n plus 3 and n plus 4 r prime so what we need is 1 n which disproves the statement so since we have a statement of the form for all X for all X we need to find an N and an example which would make this statement pause so let's go ahead and list or prime numbers from 1 up to 29 so we have two we have 3 we have 5 7 11 13 17 and 23 and 29 so we are going to try all these possible values and see which one gives us not non prime numbers so for N equals 2 we see that if we add n plus 1 then we have 3 then so that's out so for N equals 3 if we add 3 plus 2 we have 5 that's a prime so that's out so for N equals 5 if we had 5 plus 2 that 7 so that's out so for n is equal to 7 if we had 7 plus 4 then that's 11 so 7 is out and for n is equal to 11 11 plus 2 is out so for n is equal to 13 n plus 4 is 17 so that's out and for n is equal to 17 we have n plus 1 is at 18 n plus 2 is equal to 19 and plus 320 and n plus 4 is equal to 21 and therefore 2 for n is equal to 70 so therefore we have found an N which makes the statement false and so by a counter example why count example we have found we have proven rather that the statement is false