Reviewing vectors...

[Martoman]

So i'm looking through checkpoints and I see this 3 mark question on linear dependence.

Consider vectors a = -3i +2j +3k, b = -2i -2j + k and c = mi + nk. Find m/n so that a,b,c form a linearly dependent set of vectors.

My thinking is that if we want a linear dependent set we form a triangle of the vectors, so that they will end up back at zero after we add them together.

So simply a + b = -5i + 4k

But to form the triangle and get back where we started, we want the c vector to be 5i - 4k.

Then -5/4 as required.

But.there.are.three.marks.

In my working this required 2 lines of working. Someone help me here as to the marking scheme?

[superflya]

thats how i'd do it

u would add in the a + b + c = 0, theres an extra line for u :/

[pooshwaltzer]

a + b = -5i + 4k .... 1 mark
c = mi + nk = 5i - 4k .... 1 mark
m/n = undefined .... 1 mark

[Martoman]

LOOOL as if thats 3 marks!!!!!!!!!!!!! Thats my point!

They wouldn't expect us to be really azn and formulaic would they.............