Q64 / 160 · WBJEE 2009 · Mathematics
If $x^2+y^2=1$ then
- A$y y^{\prime \prime}-\left(2 y^{\prime}\right)^2+1=0$
- Correct answerB$y y^{\prime \prime}+\left(y^{\prime}\right)^2+1=0$
- C$y y^{\prime \prime}-\left(y^{\prime}\right)^2-1=0$
- D$y y^{\prime \prime}+\left(2 y^{\prime}\right)^2+1=0$
Solution
Hints: $2 x+2 y y^{\prime}=0$
$$
\begin{aligned}
& x+y y^{\prime}=0 \\
& 1+y y^{\prime \prime}+\left(y^{\prime}\right)^2=0
\end{aligned}
$$
Hence, the correct answer is option: 'B'.