You very much have to learn the ins and outs of any CAS. That said, they can be very useful dealing with large multi-term expressions, or double-checking your

You very much have to learn the ins and outs of any CAS. That said, they can be very useful dealing with large multi-term expressions, or double-checking your work by hand, playing around with transforms, etc. It's a tool though, and more about the insights you bring to it, than it brings to you if that makes sense.