MCQ
If $\bar{a}, \bar{b}, \bar{c}$ are non- coplanar vectors, then $\left[\begin{array}{lll}\overline{ a }+2 \overline{b} & \overline{ a }+\overline{ c } & \overline{ b }\end{array}\right]=$
  • A
    $0$
  • B
    $[\overline{ a } \overline{ b } \overline{ c }]$
  • $-[\overline{ a } \overline{ b } \overline{ c }]$
  • D
    $2[\overline{ a } \overline{ b } \overline{ c }]$

Answer

Correct option: C.
$-[\overline{ a } \overline{ b } \overline{ c }]$
(C) $\left[\begin{array}{lll}\overline{ a }+2 \overline{b} & \overline{ a }+\overline{ c } & \overline{ b }\end{array}\right]$
$=\left[\begin{array}{lll}\overline{ a } & \overline{ a }+\overline{ c } & \overline{ b }\end{array}\right]+\left[\begin{array}{lll}2 \overline{b} & \overline{ a }+\overline{ c } & \overline{ b }\end{array}\right]$
$=[\overline{ a } \overline{ a } \overline{ b }]+[\overline{ a } \overline{ c } \overline{ b }]+[2 \overline{b} \overline{ a } \overline{ b }]+[2 \overline{b} \overline{ c } \overline{ b }]$
$\begin{array}{l}=0-[\overline{ a } \overline{ b } \overline{ c }]+2(0)+2(0) \\ =-[\overline{ a } \overline{ b } \overline{ c }]\end{array}$

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