Respuesta :

21.9089 is the geometric mean..
the geometric mean of n numbers is the nth root of the product of those numbers

so the geometric mean of the 2 numbers, 4 and 120, is the 2nd root or square root of the product of 4 and 120

basically
the gemetric mean is the square root of 4*120=480
geometric mean=√480=4√30
the geometric mean of 4 and 120 is 4√30