JEE Main202623 January 2026Morning ShiftMathematicsVector AlgebraActual

Let a =- i + j +2 k , ~b = i - j -3 k , c = a b and d = c a . Then ( a - b ) d is equal to :

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Correct answer

D. -2

Step-by-step solution

c = a b = vmatrix i & j & k -1 & 1 & 2 1 & -1 & -3 vmatrix = (-1, -1, 0) . d = c a = vmatrix i & j & k -1 & -1 & 0 -1 & 1 & 2 vmatrix = (-2, 2, -2) . a - b = (-2, 2, 5) . ( a - b ) d = (-2)(-2) + (2)(2) + (5)(-2) = 4 + 4 - 10 = -2 .

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