Really I have never heard that before.
These lines are spoken by a captain who has been wounded in the war. He is relaying the information about Macbeth's brave fight against the enemy to King Duncan. He talks about how brave and valiant Macbeth was, so the audience can infer that he is a fierce warrior who will stop at nothing to ensure his win in a battle.
The saying means what is considered good is in fact bad and what is considered bad is actually good.
an example could be you trust someone and they seem to be a good person but looks are deceiving and they turn out to be bad
Answer:
You should take the exam, however you'll need to study hard for it.
