OAN, OMB and APB are straight lines - Edexcel - GCSE Maths - Question 21 - 2017 - Paper 3
Question 21
OAN, OMB and APB are straight lines.
AN = 2OA.
M is the midpoint of OB.
OA = a
OB = b
AP = kAB where k is a scalar quantity.
Given that MPN is a straight line... show full transcript
Worked Solution & Example Answer:OAN, OMB and APB are straight lines - Edexcel - GCSE Maths - Question 21 - 2017 - Paper 3
Step 1
Find vector expression for M
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Answer
Since M is the midpoint of OB, we can express the vector OM in terms of OA and OB:
OM=21(OA+OB)=21(a+b)
Step 2
Express MP using vectors
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Answer
The vector MP can be found as follows:
MP=O+P−OM=A+P−21(A+B)=AP+(P−21B)
This will provide the components in terms of A and B.
Step 3
Find relationship using straight line condition
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Answer
Since MPN is a straight line, there exists a scalar relationship:
If we express NP in terms of the vectors, we can say:
NP=k⋅MP
This gives the scalar multiple relationship in line.
Step 4
Conclusion for value of k
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By evaluating the vectors and balancing the components: