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J & K CET Engineering J and K - CET Engineering Solved Paper-2010

  • question_answer
    The radius of the sphere \[|\,3\,\vec{r}+2\hat{i}-\hat{j}-4\hat{k}|=3\] is

    A)  \[2\]             

    B)  \[3\]

    C)  \[1\]             

    D)  \[9\]

    Correct Answer: C

    Solution :

    Given,  sphere is \[|3\,\vec{r}+2\hat{i}-\hat{j}-4\hat{k})|=3\] \[\Rightarrow \] \[3\left| \vec{r}-\left( -\frac{2}{3}\hat{i}+\frac{1}{3}\hat{j}+\frac{4}{3}\hat{k} \right) \right|=3\] \[\Rightarrow \] \[\left| \vec{r}-\left( -\frac{2}{3}\hat{i}+\frac{1}{3}\hat{j}+\frac{4}{3}\hat{k} \right) \right|=1\]


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