Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
JEE Main201910 Jan 2019Morning ShiftMathematicsVector AlgebraActual

Let a → = 2 i ^ + λ 1 j ^ + 3 k ^ , b → = 4 i ^ + 3 - λ 2 j ^ + 6 k ^ and c → = 3 i ^ + 6 j ^ + λ 3 - 1 k ^ be three vectors such that b → = 2 a → and a → is perpendicular to c → . Then a possible value of λ 1 , λ 2 , λ 3 is

Options

  1. A- 1 2 ,   4 ,   0
  2. B1 , 5 , 1
  3. C1 2 ,   4 , - 2
  4. D1 , 3 , 1

Correct answer

A. - 1 2 ,   4 ,   0

Step-by-step solution

Since b → = 2 a → , so 3 - λ 2 = 2 λ 1 λ 2 = 3 - 2 λ 1       . . . 1 We know that if two vectors a 1 i ^ + b 1 j ^ + c 1 k ^ and a 2 i ^ + b 2 j ^ + c 2 k ^ are perpendicular, then a 1 a 2 + b 1 b 2 + c 1 c 2 = 0 Since, a → is perpendicular to c → so 6 + 6 λ 1 + 3 λ 3 - 1 = 0 ⇒ 6 + 6 λ 1 + 3 λ 3 - 3 = 0 ⇒ λ 3 = - 1 - 2 λ 1     . . . 2 From equations 1 and 2 , we get λ 1 ,   λ 2 ,   &#95

Practice Vector Algebra on Quantrex Academy →

More from Vector Algebra

Let a , b be two vectors, and let P, Q and R be the points with position vectors a , b and a + b , respectively, with respect to the origin O . If | a + b | = 21 , | a - b | = 3 , 2026Let a = 4 i - j + 3 k , b = 10 i + 2 j - k and a vector c be such that 2( a b ) + 3( b c ) = 0 . If a c = 15 , then c ( i + j -3 k ) is equal to: 2026Let a = 2 i + 3 j + 3 k and b = 6 i + 3 j + 3 k . Then the square of the area of the triangle with adjacent sides determined by the vectors (2 a + 3 b ) and ( a - b ) is : 2026If a = i + j + k , b = j - k and c be three vectors such that a c = b and a c = 3 , then c ( a - 2 b ) is equal to _______. 2026Let O be the origin, OP = a and OQ = b . If R is the point on OP such that OP = 5 OR , and M is the point such that OQ = 5 RM , then PM is equal to : 2026Let a = 7 i + j - k and b = j + 2 k . If r is a vector such that r a + a b = 0 and r a = 0 , then |3 r |^2 is equal to: 2026Let u and v be unit vectors inclined at an acute angle such that | u v |= 3 2 . If A = u + v +( u v ) , then is equal to: 2026Let a_k = ( _k) i + j and b_k = i - ( _k) j , where _k = 2^ k-1 2^n + 1 , for some n N , n > 5 . Then the value of _ k=1 ^ n | a_k |^2 _ k=1 ^ n | b_k |^2 is _____. 2026 Full Vector Algebra list All JEE Main PYQs