If the vectors, p → = a + 1 i ^ + a j ^ + a k ^ , q → = a i ^ + a + 1 j ^ + a k ^ and r →…

If the vectors, p=a+1i^+aj^+ak^,q=ai^+a+1j^+ak^ and r=ai^+aj^+a+1k^aR are coplanar and 3p.q2-λr×q2=0 , then the value of λ is ________

Solution

a+1aaaa+1aaaa+1=0a+1+a+a=0a=-13
P=23i^-13j^-k^
Q=13-i^+2j^-k^
R=13-i^-j^+2k^
P.Q=19-2-2+1=-13
R×Q=19ijk-12-1-1-12=19i4-1-j-2-1+k1+2=193i+3j+3k=i+j+k3
R×Q=133R×Q2=13 3P.Q2-λR×Q2=0
3.19-λ.13=0λ=1

Asked in: JEE Main 2020 (09 Jan Shift 1)

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