算la..
以我幫人補習ge經驗
我真係唔應該火ge..
而家教logic ge野
(再講一次..
呢part not important..
defination ge野知就得..
唔駛"明"
你係男仔..
但係你唔會知點解男仔叫做男仔
點解男係咁寫..= =
outcome都唔駛死記..
你打機充其量都係記攻略..
可以記點樣先贏
但係冇人會記自己輸定係贏= =)
遲d計數就係新景象lo..

而家好想重拾昔日睇課外書ge習慣..
但係發現時間係極度不足..
轉眼間而家就嚟十點la= =

係..
時間會好快過..

p.s.如果有人仲係唔明咩叫necessary condition 同埋sufficient condition
可以睇呢個link
http://en.wikipedia.org/wiki/Necessary_and_sufficient_conditions

佢解得好好..
being a mammal is necessary but not sufficient to being human, and that a number q is rational is sufficient but not necessary to q‘s being a real number.

兩句statement 分別係
being human impile being a mammal
a nubmer q is rational impile q is a real number

如果being human, being a mammal 係必定..
但係being a mammal冇充份理據話個樣野係human..

同樣..
number q is rational 充份講出q is a real number
但係being a real number唔必定係rational..

書裡面話
如果p impile q..
q is necessary condition
因為when q is false
p 必定係false..
如果個樣野唔係mammal ge
佢一定唔係human..

p is sufficient
因為如果我地知p 岩ge話
我地有充份理據知道q一定係岩
如果q is a rational number ge話
我地有充份理據話q is real係岩 

其實有充份理據同埋必定意思差唔多..
只係前後subject倒轉連帶要講ge野倒轉
至於點解一個係necessary一個係sufficient
只係邊個做主動咁解..
not so important..