BCECE Engineering BCECE Engineering Solved Paper-2010

  • question_answer
    The vector equation of a plane through the point \[(2\hat{i}-\hat{j}-4\hat{k})\] and parallel to the plane \[\vec{r}.(4\hat{i}-12\hat{j}-3\hat{k})-7=0\]is

    A) \[\vec{r}.(4\hat{i}-12\hat{j}-3\hat{k})=0\]

    B)                  \[\vec{r}.(4\hat{i}-12\hat{j}-3\hat{k})=32\]

    C)                  \[\vec{r}.(4\hat{i}-12\hat{j}-3\hat{k})=12\]

    D)  None of the above

    Correct Answer: B

    Solution :

    The equation of plane parallel to- the plane \[\vec{r}.(4\hat{i}-12\hat{j}-3\hat{k})-7=0\]is \[\vec{r}.(4\hat{i}-12\hat{j}-3\hat{k})+\lambda =0\]       ?(i) But the plane Eq. (i) passes through\[2\hat{i}-\hat{j}-4\hat{k}.\] \[\therefore \]  \[(2\hat{i}-\hat{j}-4\hat{k}).(4\hat{i}-12\hat{j}-3\hat{k})+\lambda =0\] \[\Rightarrow \]\[8+12+12+\lambda =0\] \[\Rightarrow \]\[\lambda =-32\] So, the required plane is                 \[\vec{r}.(4\hat{i}-12\hat{j}-3\hat{k})-32=0\]


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