Let veca and vecb be two vectors, Let | veca|=1,| vecb|=4 and veca ⋅ vecb=2. If vecc=(2 veca × vecb)-3 vecb, then the value of vecb ⋅ vecc is

Question

Let veca and vecb be two vectors, Let | veca|=1,| vecb|=4 and veca ⋅ vecb=2. If vecc=(2 veca × vecb)-3 vecb, then the value of vecb ⋅ vecc is (A) -60 (B) -48 (C) -84 (D) -24

Tardigrade Admin · Accepted Answer

vec c =(2 vec a × vec b )-3 vec b vec b ⋅ vec c = vec b ⋅(2 vec a × vec b )-3 vec b ⋅ vec b =-3| b |2 =-48

Q. Let $a$ and $b$ be two vectors, Let $∣ a ∣ = 1, ∣ b ∣ = 4$ and $a \cdot b = 2$ . If $c = (2 a \times b) - 3 b$ , then the value of $b \cdot c$ is

$- 60$

$- 48$

$- 84$

$- 24$

$c = (2 a \times b) - 3 b$
$b \cdot c = b \cdot (2 a \times b) - 3 b \cdot b$
$= - 3∣ b ∣^{2}$
$= - 48$

Q. Let a and b be two vectors, Let ∣a∣=1,∣b∣=4 and a⋅b=2. If c=(2a×b)−3b, then the value of b⋅c is

−60

−48

−84

−24