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If you get a piece paper, look at the question being asked, and solve it using a pencil, you'll get the the answer to the question.
It tells you the order in which the equation needs to be simplified.
Showing the question would help to solve it.
If you are dealing with the square root of negative numbers you are at a level of maths that is advanced enough for you to be able to answer such a basic question. The fact that you do not know the answer to the question suggests that you are not yet studying complex numbers. That being the case, there is something wrong with the question.
A formula is math sentence where you substitute numbers for letters and solve to get an unknown value.