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QJEEM24Mabbf5: JEE Main 2024 Mathematics - Class 12 JEEM24Mabbf5 Solution: Suppose the solution of the differential equation represents a…

Suppose the solution of the differential equation dydx=(2+α)x−βy+2βx−2αy−(βγ−4α)\frac{d y}{d x}=\frac{(2+\alpha) x-\beta y+2}{\beta x-2 \alpha y-(\beta \gamma-4 \alpha)} represents a circle passing through origin. Then the radius of this circle is :

Multiple Choice Options

  • A 17\sqrt{17}
  • B 2
  • C 172\frac{\sqrt{17}}{2}
  • D 12\frac{1}{2}

Step-by-Step Verified Solution

amp;dydx=(2+α)x−βy+2βx−2αy−(βγ−4α)amp;βxdy−2αydy−(βγ−4α)dyamp;=2xdx+αxdx−βydx+2dxamp;β∫(xdy+ydy)−αy2−(βγ−4x)y=x2+αx22+2xamp;βxy−αy2−(βγ−4α)y=x2+αx22+2xamp;(1+α2)x2+αy2−βxy+2x+(βγ−4α)y=0amp;∵ this represents circle passing through origin amp;⇒β=0 and 1+α2=αamp;⇒α=2\begin{aligned}& \frac{d y}{d x}=\frac{(2+\alpha) x-\beta y+2}{\beta x-2 \alpha y-(\beta \gamma-4 \alpha)} \\& \beta x d y-2 \alpha y d y-(\beta \gamma-4 \alpha) d y \\& =2 x d x+\alpha x d x-\beta y d x+2 d x \\& \beta \int(x d y+y d y)-\alpha y^2-(\beta \gamma-4 x) y=x^2+\frac{\alpha x^2}{2}+2 x \\& \beta x y-\alpha y^2-(\beta \gamma-4 \alpha) y=x^2+\frac{\alpha x^2}{2}+2 x \\& \left(1+\frac{\alpha}{2}\right) x^2+\alpha y^2-\beta x y+2 x+(\beta \gamma-4 \alpha) y=0 \\& \because \text { this represents circle passing through origin } \\& \Rightarrow \beta=0 \text { and } 1+\frac{\alpha}{2}=\alpha \\& \Rightarrow \alpha=2\end{aligned}

amp;∴C:2x2+2y2+2x−8y=0amp;x2+y2+x−4y=0amp; Radius =14+4−0amp;=172\begin{aligned}& \therefore C: 2 x^2+2 y^2+2 x-8 y=0 \\& x^2+y^2+x-4 y=0 \\& \text { Radius }=\sqrt{\frac{1}{4}+4-0} \\& \quad=\frac{\sqrt{17}}{2}\end{aligned}

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