The mad is 9
the mean is 4.5
then calculate all differences and you get 9
5 and 4 digit only Po that's the answers
Answer: 
-3 times the square root of 5
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Explanation:
Let 
Replace all the root 5 terms with x and we go from

to

From here, combine like terms to get

and the last thing to do is replace the x with sqrt(5)

Meaning that,

