JEE Main 2014MathematicsVector AlgebraEasyMCQ

JEE Main 2014 — Vector Algebra Question with Solution

JEE Main 2014 (09 Apr Online)

Question

If a→=2, b→=3 and 2a→-b→=5, then 2a→+b→ equals :

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Show full solutionCorrect option: A
Correct answer
A5

Step-by-step explanation

a→=2,  b→=3,  2a→-b→=5

2 a→-b→2=2 a→-b→·2 a→-b→

=4a→2-4a→·b→+b→2      ...i

2a→+b→2=4a→2+4a→·b→+b→2    ...ii

Adding equation (i) and equation (ii), we get

2 a→+b→2+2 a→-b→2=8a→2+2b→2

⇒  2 a→+b→2+52=822+232

⇒ 2a→+b→2=32+18-25 = 2 5

⇒   2a→+b→=5

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About this question

This is a previous-year question from JEE Main 2014, covering the Vector Algebra chapter of Mathematics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.