回答: #|| C || = sqrt(98)# 説明: #A =(4、-5,2) "" B =(9,3、-1)# #デルタx = B x -A x = 9-4 = 5# #Delta y = B_y-A_y = 3 + 5 = 8# #Delta z = B_z-A_z = -1-2 = -3# #|| C || = sqrt(5 ^ 2 + 8 ^ 2 +( - 3)^ 2)# #|| C || = sqrt(25 + 64 + 9)# #|| C || = sqrt(98)#