I suppose. There's more leniency in other questions in your working out but in "Show" or "Prove" questions you have to carry the marker through your thought process to effectively answer the question, it really depends on how lenient your teacher is on such questions so if they're fine with you skipping some steps such as showing z + z conjugate is 2Re(z) = 2cos(z) then more time saved. That's just what my teacher tells me so take it with a grain of salt - when I do excercise questions I don't bother going the full way since it becomes repetitive but in practice exams I do go the full way of showing.