Questions & Answers about Je suis monté sur la pente et j'ai descendu le câblage.
Why does the first verb use être (suis monté) while the second uses avoir (ai descendu)?
Both monter and descendre are verbs of motion that normally take être in the passé composé. However, when they have a direct object (meaning you are moving something else), they switch to using avoir. Here, you went up yourself (no object, so it takes être), but you took the wiring down (le câblage is the direct object, so it takes avoir).
Could j'ai descendu le câblage also mean I went down the wiring?
Why use sur after monté instead of just saying Je suis monté la pente?
You cannot use être with a direct object. If you wanted to treat the slope as a direct object (I climbed the slope), you would actually have to switch to avoir and say J'ai monté la pente. By using être (Je suis monté) plus the preposition sur, it means you went up onto the slope. Both convey a similar idea but require different grammatical structures.