Let x_0 be the point of local maxima of f(x)= a ( b c ), where a =x i -2 j +3 k , b =-2 i +x j - k and c =7 i...

Question

Let x_0 be the point of local maxima of f(x)= a ( b c ), where a =x i -2 j +3 k , b =-2 i +x j - k and c =7 i -2 j +x k . Then the value of a b + b c + c a at x = x_0 is :

Accepted Answer

(C)

JEE Main 2020 Mathematics question

Solution