Let a → = i ^ + 5 j ^ + α k ^ ,   b → = i ^ + 3 j ^ + β k ^ and c → = - i ^…

Let a=i^+5j^+αk^, b=i^+3j^+βk^ and c=-i^+2j^-3k^ be three vectors such that, |b×c|=53 and a is perpendicular to b. Then the greatest amongst the values of |a|2 is ________.

Solution

a·b=0

1+15+αβ=0

αβ=-16    ...(1)

Also, 

b×c2=75

10+β2·14-5-3β2=75

5β2+30β+40=0

β=-4, -2

α=4, 8

amax2=26+α2max=90

Asked in: JEE Main 2021 (27 Aug Shift 1)

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