BCECE Engineering BCECE Engineering Solved Paper-2010

  • question_answer
    Observe the following statements: (i) The   circle  \[{{x}^{2}}+{{y}^{2}}-6x-4y-7=0\] touches y-axis (ii) The   circle   \[{{x}^{2}}+\text{ }{{y}^{2}}+6x+4y-7=0\] touches \[x-\]axis Then, which of the following statements is/are correct?

    A)  Both I and II    

    B)         Neither I nor II

    C)                         Only I                  

    D)         Only II

    Correct Answer: B

    Solution :

    I. We have the equation of circle \[{{x}^{2}}+{{y}^{2}}-6x-4y-7=0\] Here,\[g=-3,\]\[f=-2,\]  \[c=-7\] Condition that the circle touches y-axis is                                 \[{{f}^{2}}=c\] But for the given circle, this condition does not follow, since                 \[{{f}^{2}}\ne c\]                                              \[[\because \,{{(-2)}^{2}}\ne -7]\] Hence, the circle does not touch y-axis. II. The equation of circle is \[{{x}^{2}}+{{y}^{2}}+6x+4y-7=0\] Here, \[g=3,\,f=2,\,c=-7\] We know, the condition that the circle touches \[x-\]axis is                                 \[{{g}^{2}}=c\] But for the given circle, this condition does not follow, since \[{{g}^{2}}\ne c\]                             \[[\because \,({{3}^{2}})\ne -7]\] Hence, the circle does not touch \[x-\]axis.


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