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# Perpendicular Vectors Question Watch

1. OP and OQ are two position vectors such that OP= r - s and OQ= 2r + 3s
Given that OP is perpendicular to OQ, then r•s is equal to?

I'm a bit confused about the question asking for r • s. I'm accustomed to the question asking for OP • OQ. Does this r • s work the same way if not, can someone provide me with a solution (explanation optional, I could try to work my way to the solution)
2. OP•OQ=(r-s)•(2r+3s).
Expand this as you normally would but keep the dot in between each letter. Hope this makes sense.

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Updated: June 5, 2016
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