CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2009

  • question_answer
    The   vector   form   of   the   sphere\[2({{x}^{2}}+{{y}^{2}}+{{z}^{2}})-4x+6y+8z-5=0\]is

    A)  \[\overrightarrow{r}.[\overrightarrow{r}-(2\hat{i}+\hat{j}+\hat{k})]=\frac{2}{5}\]

    B)  \[\overrightarrow{r}.[\overrightarrow{r}-(2\hat{i}-3\hat{j}-4\hat{k})]=\frac{1}{2}\]

    C)  \[\overrightarrow{r}.[\overrightarrow{r}-(2\hat{i}+3\hat{j}+4\hat{k})]=\frac{5}{2}\]

    D)  \[\overrightarrow{r}.[\overrightarrow{r}+(2\hat{i}-3\hat{j}-4\hat{k})]=\frac{5}{2}\]

    E)  \[\overrightarrow{r}.[\overrightarrow{r}-(2\hat{i}-3\hat{j}-4\hat{k})]=\frac{5}{2}\]

    Correct Answer: E

    Solution :

    Given equation can be rewritten as \[{{x}^{2}}+{{y}^{2}}+{{z}^{2}}-2x+3y+4z-\frac{5}{2}=0\] Let        \[\overrightarrow{r}=x\hat{i}+y\hat{j}+z\hat{k}\] \[\therefore \]Given equation written in vector form is                 \[\overrightarrow{r}.[\overrightarrow{r}-(2\hat{i}-3\hat{j}-4\hat{k})]=\frac{5}{2}\]


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