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Need solution for  RD Sharma maths Class 12 Chapter 21 Differential Equation Exercise Multiple choice Question Question 46 textbook solution.

Answers (1)

Answer : (c) \frac{d^{2} y}{d x^{2}}-x^{2} \frac{d y}{d x}+x y=0

Hint : Check each options one by one .

Given : y=x

Explanation : y=x

\begin{aligned} &\Rightarrow \frac{d y}{d x}=1 \\ &\Rightarrow \frac{d^{2} y}{d x^{2}}=0 \end{aligned}

Now, option  (a)\frac{d^{2} y}{d x^{2}}-x^{2} \frac{d y}{d x}+x y=x

\begin{aligned} &\text { LHS }=0-x^{2} \times 1+x \times x \\ &=-x^{2}+x^{2}=0 \neq x \end{aligned}

Option \text { (b) } \frac{d^{2} y}{d x^{2}}+x \frac{d y}{d x}+x y=x

\begin{aligned} &\text { LHS }=0+x \times 1+x \times x=x \\ &=x+x^{2} \neq x \end{aligned}

Option \text { (c) } \frac{d^{2} y}{d x^{2}}-x^{2} \frac{d y}{d x}+x y=0

\begin{aligned} &\text { LHS } \\ &\qquad \begin{array}{l} =0-x^{2} \times 1+x \times x \\ =-x^{2}+x^{2} \\ =0=\mathrm{RHS} \end{array} \end{aligned}

Hence, the correct option is (c)

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