If the vectors a→ + λb→ +&thins

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 Multiple Choice QuestionsMultiple Choice Questions

521.

If vectors i^ + j^ + k^, i^ - j^ + k^ and 2i^ + 3j^ + λk^ are coplanar, then λ is equal to

  • - 2

  • 3

  • 2

  • - 3


522.

Given, a  ba = 1 and if a  + 3b2a - b = - 10b is equal to

  • 1

  • 3

  • 2

  • 4


523.

a + b b + c c + a = a b c, then

  • a b c = 1

  • a b c are coplanar

  • a b c = - 1

  • a b c are mutually perpendicular


524.

Area of rhombus is ..., where diagonals are a = 2i^ - 3j^ + 5k^ and  b = - i^ + j^ + k^

  • 21.5

  • 31.5

  • 28.5

  • 38.5


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525.

a . b × cb . c × a + b . a × ba . b ×c  is equal to

  • 1

  • 2

  • 0


526.

If a = b = 1 and a + b = 3, then the value of 3a - 4b . 2a +5b is

  • - 21

  • - 212

  • 21

  • 212


527.

If a is perpendicular to b and ca = 2, b = 3, c = 4 and the angle between b and c is 2π3, then [a b c] is equal to

  • 43

  • 63

  • 123

  • 183


528.

If ab and c are perpendicular to b +cc +a and a +b respectively and if a + b = 6, b + c = 8 and c + a = 10 then a + b + c is equal to

  • 52

  • 50

  • 102

  • 10


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529.

If the vectors a +λb +3c- 2a +3b -4c and a -3b +5c are coplanar, then the value of λ is

  • 2

  • - 1

  • 1

  • - 2


D.

- 2

Since, the given three vectors are coplanar, therefore one of them should be expressible as a linear combination of the remaining two ie, there exist two scalars x and y such that

a +λb +3c = x- 2a +3b -4c + ya -3b +5c

On comparing the coefficient of  a, b and c on both sides, we get

          2x + y = 1 ; 3x - 3y = λ

and - 4x + 5y = 3

On solving first and third equations, we get

x = - 13, y = 13

Since, the vectors are coplanar, therefore these values of x and y, also satisfy the second equation ie, - 1 - 1 = λ

 λ = - 2


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530.

If a + b + c = 0a = 3, b = 5, c = 7, then anle between a and b is

  • π6

  • 2π3

  • 5π3

  • π3


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