The past subjunctive: regular -ar verbs
The past subjunctive of regular -ar verbs is generally formed as follows:
(For the time being, we ignore the alternative past subjunctive form ending in -se used in some varieties of Spanish. As we'll see later, this form is trivially predictable once you know the -ara/-iera past subjunctive forms.)
The last point means that in the written form, the three-syllable nosotros form is -áramos with a written accent on the first e. The ending doesn't need a written accent in the other persons, but in terms of pronunciation, the stressed syllable is always that with the first a of the past subjunctive ending: (que) preguntaras, (que) tomarais etc.
Spelled out in full, this gives the following endings and example past subjunctive forms of the verb llegar (to arrive):
Next: past subjunctive of other verbs
As we'll see on the next page, the past subjunctive of non-ar verbs is based on a slightly different ending, although the overall forms are similar.