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Explain solution RD Sharma class 12 Chapter 11 Higher Order Derivatives Exercise Multiple Choice Question question 24

Answers (1)

Answer:

                (a)

Hint:

We must know about the derivative of logarithm.

Given:

                y=x^{n-1} \log x

Explanation:

                  y=x^{n-1} \log x

                 \\ \frac{d y}{d x}=y_{1}=(n-1) x^{n-2} \log x+\frac{x^{n-1}}{x} \\

                \begin{aligned} & &y_{1}=\frac{(n-1) x^{n-1} \log x+x^{n-1}}{x} \end{aligned}

                x y_{1}=(n-1) y+x^{n-1} \\                                                                                                     \left[\because y=x^{n-1} \log x\right]

                x y_{2}+y_{1}=(n-1) y_{1}+(n-1) x^{n-2}

                \begin{aligned} & \\ &x y_{2}+y_{1}=(n-1) y_{1}+\frac{(n-1) x^{n-1}}{x} \end{aligned}                                                                                                      

                x^{2} y_{2}+x y_{1}=x(n-1) y_{1}+(n-1) x^{n-1}          

                \\ x^{2} y_{2}+x y_{1}=x(n-1) y_{1}+(n-1)\left[x y_{1}-(n-1) y\right] \\                                                                                                                     

                x^{2} y_{2}+x y_{1}=x(n-1) y_{1}+(n-1) x y_{1}-(n-1)^{2} y \\

                \begin{aligned} & &x^{2} y_{2}+x y_{1}=2 x(n-1) y_{1}-(n-1)^{2} y \end{aligned}

                x^{2} y_{2}+x y_{1}-2 x(n-1) y_{1}=-(n-1)^{2} y \\

                x^{2} y_{2}+x y_{1}(1-2 n+2)=-(n-1)^{2} y \\

                \begin{aligned} & &x^{2} y_{2}+(3-2 n) x y_{1}=-(n-1)^{2} y \end{aligned}

 

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