Question

Vectors

A = 3i - 2j + 4k
B = -5i + 2j - k


A x 4B = -24i-68j-16k

PLEASE VERIFY ?

Answer 1

A=3i-2j+4k
4B=-20i+8j-4k

i j k
3 -2 4
-20 8 -4
+8i-80j+24k-32i+12j-40k
-24i-68j-16k

Yep.

Answer 2

Then why my teacher gets this ? http://screencast.com/t/mAWmT5bH

Answer 3

You sure the B is -5i+2j-k instead of -5i+2j-4k ?

Answer 4

bro notice A x 4B = -24i-68j-16k notice the 4B..

Answer 5

well your teacher wrote down
\[d _{1}\times 4d_{2}=(3i-2j+4k)\times(-20i+8j-16k)\]
So I assume he wrote wrong.

Answer 6

i would have to agree with zhantshen, clearly -16k should be -4k with the numbers that you gave

Answer 7

http://www.wolframalpha.com/input/?i=%3C3%2C+-2%2C+4%3E+cross+4%3C-5%2C+2%2C+-1%3E