Question

Let
A=i+3j−2k
and
B=4i−2j+4k
, find
(2A+B)(˙A−2B)
-14
-21
-10
-5

Answer 1

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Answer on Question #56117 – Math – Vector Calculus

Let A=i+3j-2k and B=4i-2j+4k, find (2A+B)(^A-2B)

-14

-21

-10

-5

Solution

2A=2i+6j-4k;

2B=8i-4j+8k;

$$(2A+B)(A-2B) = (2i+6j-4k+4i-2j+4k)(i+3j-2k-8i-4j+8k) = (6i+4j)(-7i+7j-10k) = 6^(-7) + 4^7 + 0^10 = -42 + 28 = -14.$$

Answer: -14.