Question

If Ā=9î-7j+5k and B = 3î - 2j-6k
then the value of (A+B). (A-B) is
1)206
2)128
3)106
4)-17
.​

Answer 1

Answer:

3) 106

Explanation:

Given; A=(9,-7,5) , B=(3,-2,-6)

(A+B) = (9+3, [-7]+[-2] ,5-6) = (12, -9, -1)

(A-B) = (9-3, (-7)-(-2) , 5-[-6]) = (6, -5, 11)

(A+B).(A-B) = (12*6) + (-9*-5) + (-1*11) = 72+45-11=72+(34)= 106