NTA Abhyas JEE Main2020MathematicsVector AlgebraPractice
Let a → = i ^ + j ^ + k ^ , b → = 2 i ^ - 3 j ^ + 4 k ^ and a → × c → = b → + 2 λ a → , then the value of a → b → c → is equal to
Options
- A12
- B26
- C- 26
- D3
Correct answer
C. - 26
Step-by-step solution
a → × c → = b → + 2 λ a → Taking dot product with a → 0 = b → ⋅ a → + 2 λ a → ⋅ a → ⇒ 0 = 3 + 6 λ ⇒ λ = - 1 2 i.e. a → × c → = b → - a → Taking dot product with b → a → × c → ⋅ b → = b → ⋅ b → - a → ⋅ b → ⇒ a → c → b → = 29 - 3 ⇒ a → b → c → = - 26