MCQ
If $\bar{c}=2 \bar{a}-3 \bar{b}$ and $2 \bar{c}=3 \bar{a}+4 \bar{b}$, then $\bar{c}$ and $\bar{a}$ are
  • like parallel vectors
  • B
    unlike parallel vectors
  • C
    at right angles
  • D
    none of these

Answer

Correct option: A.
like parallel vectors
(A) Given $\overline{ c }=2 \overline{ a }-3 \overline{b}$ ...(i)
and $2 \overline{ c }=3 \overline{ a }+4 \overline{b}$ ...(ii)
Multiplying (i) by 4 and (ii) by 3 and adding,
we get
$10 \overline{ c }=17 \overline{ a }$
$\Rightarrow \overline{ c }=\frac{17}{10} \overline{ a }$
Since $\bar{c}$ and $\bar{a}$ are in the same direction.
$\therefore \quad \overline{ c }$ and $\overline{ a }$ are like parallel vectors.

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