Let's get started. 請問為用started,或應用start,另 I saw my friend get killed in front of me.可以理解get為連綴動詞后用killed構成被動語態.謝謝?

"Get started" - 是一種慣用語，表示開始做某件事情。
~ Let's get started.
~ I think we should get started.

如果要用start，一般要加上受詞，如:
~ Let's start the job.
~ Let's start cooking the dinner.

I saw my friend get killed in front of me.
sense verb (saw) + object (my friend) + bare infinitive (get)

get作為連綴動詞，有两種演繹方式:
(1) get + 形容詞  (同義詞 = become)
例:  get angry: get married; get excited; get bored ....
(2) get + 過去分詞  (構成被動語態; 也有形容詞的性質)
例:  get killed; get hurt; get shouted at; get stolen ....

用started. 這是在口語中的用法. 比較正式的說法是Let's start.

is killed或get killed都可以. get killed是比較不正式(informal)的用法. 但通常對文法比較挑的人會避免用get/got.