Its runway is 72 feet below sea level a passenger in a small airplane on the runway holds her phone exactly 4 feet above the runway

answer: i think it is (1,-2)

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.