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Question
Find the position vector of the point which divides the join of points with position vectors `vec"a" + 3vec"b" and vec"a"- vec"b"` internally in the ratio 1 : 3.
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Solution
Required position vector is `(1(vec"a" - vec"b") + 3(vec"a" + 3vec"b"))/(1 + 3)`
= `(1(vec"a" - vec"b") + 3(vec"a" + 3vec"b"))/(4)`
= `vec"a" + 2vec"b"`.
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