Question

If a =9i-7j+5k and b=3i-2j-6k then the value of (a+b).(a-b)
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Answer 1

ANSWER:-

given,

a= 9i-7j+5k

&

b= 3i-2j-6k

now,

(a+b)= 12i-9j-k

and (a-b)= 6i-5j-11k

their dot product

(a+b).(a-b)

=> (12i-9j-k).(6i-5j-11k)

=>72+45+11

=>128