If a_1 and a_2 are two non collinear unit vectors and if (a_1+a_2)= 3, then the value of (a_1-a_2). (2a_1+a_2) is -

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Accepted Answer

Correct answer: C. (c) a_1=a_2=1 and a_1^2+a_2^2+2a_1a_2 cos ⁡ = ( 3 )^2=3 Or 1+1+2 cos =3 or cos = 12 Now(a_1-a_2)(2a_1+a_2)=2a_1^2-a_2^2-a_1a_2 cos =2-1- 12= 12

$If a_{1} and a_{2} are two non collinear unit vectors and if (a_{1} + a_{2}) = 3, then the value of (a_{1} - a_{2}) . (2 a_{1} + a_{2}) is -$

Solution

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