Manipal Engineering Manipal Engineering Solved Paper-2009

  • question_answer
    \[z=\tan (y+ax)+\sqrt{y-ax}\Rightarrow \,\,{{z}_{xx}}-{{a}^{2}}{{z}_{yy}}\]is equal to

    A)  0                                            

    B)  2

    C) \[{{z}_{x}}+{{z}_{y}}\]   

    D)        \[{{z}_{x}}{{z}_{y}}\]

    Correct Answer: A

    Solution :

    Given,   \[z=\tan (y+ax)+\sqrt{y-ax}\] \[\Rightarrow \]\[{{z}_{x}}={{\sec }^{2}}(y+ax)a+\frac{1}{2\sqrt{y-ax}}(-a)\] \[\Rightarrow \]\[{{z}_{xx}}=2{{\sec }^{2}}(y+ax)\tan (y+ax){{a}^{2}}\]                                                                 \[-\frac{1}{4{{(y-ax)}^{3/2}}}\] and  \[{{z}_{y}}={{\sec }^{2}}(y+ax)+\frac{1}{2\sqrt{y-ax}}\]. \[\Rightarrow \]\[{{z}_{yy}}=2{{\sec }^{2}}(y+ax)\tan (y+ax)\]                                                 \[-\frac{1}{4{{(y-ax)}^{3/2}}}\] \[\therefore \,\,{{z}_{xx}}-{{a}^{2}}{{z}_{yy}}=0\]


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