JEE Main & Advanced AIEEE Solved Paper-2005

  • question_answer
    If the plane\[2ax-3ay+4az+6=0\]passes through the mid-point of the line joining the    centres    of    the    spheres\[{{x}^{2}}+{{y}^{2}}+{{z}^{2}}+6x-8y-2z=13\] and\[{{x}^{2}}+{{y}^{2}}+{{z}^{2}}-10x+4y-2z=8,\]then a equals     AIEEE  Solved  Paper-2005

    A) 2                             

    B)        \[-2\]                    

    C)        1                             

    D)        \[-1\]

    Correct Answer: B

    Solution :

    Centre of sphere \[{{x}^{2}}+{{y}^{2}}+{{z}^{2}}+2ux+2\upsilon y+2\omega z+d=0\]is \[(-u,-\upsilon ,\omega )\]. Given equation of first sphere is \[{{x}^{2}}+{{y}^{2}}+{{z}^{2}}+6x-8y-2z=13\]             ...(i) whose centre is (-3, 4,1) and equation of second sphere is \[{{x}^{2}}+{{y}^{2}}\text{+ }{{z}^{2}}-10x+4y-2\text{ }z=8\]           .. .(ii) whose centre is (5, -2,1). Mid-point of (-3, 4,1) and (5, -2,1) is (1,1,1). Since, the plane passes through (1,1,1). \[\therefore \]                  \[2a-3a+4a+6=0\] \[\Rightarrow \]                               \[3a=-\text{ }6\Rightarrow a=-2\]


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