I do not know what {-21/2} and {-61/2}{ -21/2-5} is

answer: i realy don't get it that much can you me figer it out pleas you

step-by-step explanation:

answer: 4  

the square root of 16 is 4. it is a very simple mathematic concept. a square root when a number multiplied by itself will result in a number. here, the number 16 comes when 4 is multiplied by 4. hence the square root of 16 is 4. you can always figure out a square root by the inverse operation of squaring.