# If #A= <6 ,9 ,-1 ># and #B= <9 ,-1 ,8 >#, what is #A*B -||A|| ||B||#?

##### 1 Answer

Mar 23, 2016

#### Explanation:

#A = < color(blue)(6), color(green)(" "9), color(purple)(-1) >#

#B = < color(blue)(9), color(green)(-1), color(purple)(" "8) >#

#||A|| = sqrt(6^2 + 9^2 + (-1)^2) = sqrt(36 + 81 + 1) = sqrt(118)#

#||B|| = sqrt(9^2 + (-1)^2 + 8^2) = sqrt(81 + 1 + 64) = sqrt(146)#

In total, you have

#A * B - ||A|| * ||B|| = 37 - sqrt(118)*sqrt(146) ~~94,26#