fixed的動詞原形是什麼

例句：

The monthly fee is fixed and there are no hidden extras.

月費是固定的，沒有未言明的`額外開支。

With this type of camera, the shutter speed is fixed

對這類相機而言，快門的速度是固定的。

My parents had fixed ideas about what I should become.

父母對我應該成為什麼樣的人有定見。

His eyes were fixed on a small house in the middle distance.

他凝視着不遠處的一座小房子。

Has the date of the next meeting been fixed?

下次會議的日期確定了沒有？