JEE Main & Advanced JEE Main Paper (Held on 10-4-2019 Afternoon)

  • question_answer
    If the line \[ax+y=c,\]touches both the curves \[{{x}^{2}}+{{y}^{2}}=1\] and \[{{y}^{2}}=4\sqrt{2}\text{ }x,\]then \[|c|\]is equal to : [JEE Main 10-4-2019 Afternoon]

    A) \[1/2\]              

    B) \[2\]

    C) \[\sqrt{2}\]      

    D) \[\frac{1}{\sqrt{2}}\]

    Correct Answer: C

    Solution :

                Tangent to\[~{{y}^{2}}=4\sqrt{2}x\] is \[y=mx+\frac{\sqrt{2}}{m}\]it is also tangent to \[{{x}^{2}}+{{y}^{2}}=1\] \[\Rightarrow \left| \frac{\sqrt{2}/m}{\sqrt{1+{{m}^{2}}}} \right|=1\Rightarrow m=\pm 1\] \[\Rightarrow \]Tagent will be \[y=x+\sqrt{2}\] or \[y=-x-\sqrt{2}\]compare with \[y=ax+C\] \[\Rightarrow a=\pm 1\,\,\,\And \,\,\,C=\pm \sqrt{2}\]           


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