Question

If a = 2i - 3j + k and b = i + 4j - 2k, then find (a + b) × (a - b).

Answer 1

hope it helps you thanksssssss

Answer 2

Answer:$(\vec\:a+\vec\:b)\times (\vec\:a-\vec\:b)=-4\hat i-10\hat j-22\hat k$

solution:

$\vec a=2\hat i-3\hat j+\hat k\\\\\vec b=\hat i+4\hat j- 2\hat k\\\\\\\vec a+\vec b=3\:\hat i+\hat j-\hat k\\\\\vec a-\vec b=\hat i-7\hat j+3\hat k$

Now to find $(\vec a+\vec b)\times (\vec a-\vec b)$

$\left|\begin{array}{ccc}\hat i&\hat j&\hat k\\3&1&-1\\1&-7&3\end{array}\right| \\\\\hat i(3-7)-\hat j(9+1)+\hat k(-21-1)\\\\=-4\hat i-10\hat j-22\hat k$