Week 5

We got the first term test feed back, class average was high, and I need to work more on it.

In this week, we had introduction to universal and existence, in English is ' for all' and 'there exist' To prove universal, we need to show any elements in the set satisfies the conditions, in other words, to disprove it, we need one counter example to show that there is at least one elements in set that do not satisfy the condition. Similarly, to prove existence,  we need to show there is at least one element in set that satisfy the statement, and show no elements in set that satisfy the statement if disproving it.

Until now, proofs are not complicated.