Question

Could someone please point-out the mistake(s) I am making while trying to find the norm of the following vectors.
u=i-3j+2k
v=i+j
w=2i+2j-4k

I am asked to find:
||3u-5v+w||

(click to see my work)

Answer 1

Are you finding the magnitude?

Answer 2

=||3(i-3j+2k)-5(i+j)+(2i+2j-4k)||
=||(3i-9j+6k)-(5i+5j)+(2i+2j-4k)||
=||-2j+2k||
=2sqrt(2)

Answer 3

Answer in book:
2sqrt(37)

Answer 4

Are you finding the magnitude or not?

Answer 5

Yes
I am asked to find the norm, as stated in the original post.
Norm=magnitude=length.

Answer 6

absolute value of 2k - 12j...?

Answer 7

Notice that:\[\bf 3u-5v+w=[3,-9,6]+[-5,-5,0]+[2,2,-4]=[0,-12,2]\]Then the magnitude is:\[\bf \sqrt{(0)^2+(-12)^2+(2)^2)}=\sqrt{148}=\sqrt {4*37}=2\sqrt{37}\]

@Babyslapmafro

Answer 8

Ok, accidentally added the 5 of the second vector instead of subtracting, thanks...