ATAR Notes: Forum
VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Specialist Mathematics => Topic started by: Martoman on August 08, 2010, 11:25:56 pm
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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?
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thats how i'd do it :P
u would add in the a + b + c = 0, theres an extra line for u :/
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a + b = -5i + 4k .... 1 mark
c = mi + nk = 5i - 4k .... 1 mark
m/n = undefined .... 1 mark
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LOOOL as if thats 3 marks!!!!!!!!!!!!! Thats my point!
They wouldn't expect us to be really azn and formulaic would they............. ::)