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May 31st, 2017, 04:19 PM   #1
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Vectors: where k is a scalar quantity



Hello,

I'd really appreciate some help with this particular question on vectors. The website is not offering answers.

The question is:

In the diagram above (not drawn to scale) X is the point on AB such that AX:XB=9:4.

The position vector of A is 3a and the position vector of B is 3b.

Find the value of k if OX=k(4a+9b) where k is a scalar quantity.

Thanks so much!
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May 31st, 2017, 04:56 PM   #2
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k = 3/13
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May 31st, 2017, 05:26 PM   #3
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Find $\vec{AB}$. Then use $\vec{AX}=\frac9{13}\vec{AB}$ (why?). And finally $\vec{OX}=\vec{OA}+\vec{AX}$.
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May 31st, 2017, 11:24 PM   #4
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use of section formula:
OX = [9(3a) + 4(3b)]/(9+4) = (9a+4b)3/13
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