If I'm trying to describe a situation in the past in which I wasn't able to find a specific pair of shoes, should I say:
- I couldn't find those ones.
- I wasn't able to find those ones.
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In this specific case, "can" and "be able to" are interchangeable. But be careful, because there are subtle differences.
For example, your question start with "Can I use..." - this is an example of using "can" with the meaning "is allowed to". Consequently, "can you do it?" may have a very different meaning from "are you able to do it?", and sometimes you should choose your words carefully.