RAJASTHAN ­ PET Rajasthan PET Solved Paper-2007

  • question_answer
    The order and degree of the differential equation of the family of curve \[{{y}^{2}}=2c(x+\sqrt{c}),\]where c is a arbitrary constant, is

    A)  order 1, degree 2  

    B)  order 1, degree 1

    C)  order 1, degree 3 

    D)  order 2, degree 2

    Correct Answer: C

    Solution :

     Given, equation of family of curve is \[{{y}^{2}}=2c(x+\sqrt{c})\]             ...(i) \[2y.\frac{dy}{dx}=2c\] \[\Rightarrow \]           \[c=y.{{y}_{1}}\]                        ...(ii) From Eq. (i), \[{{y}^{2}}=2y{{y}_{1}}(x+\sqrt{y{{y}_{1}}})\] \[\Rightarrow \] \[{{y}^{2}}=2y{{y}_{1}}x+2{{(y{{y}_{1}})}^{3/2}}\] \[\Rightarrow \] \[{{({{y}^{2}}-2y{{y}_{1}}x)}^{2}}=4{{(y{{y}_{1}})}^{3}}\] Hence, order = 1 and degree = 3.


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