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Let \mathrm{y=y_{1}(x) } and \mathrm{y=y_{2}(x) } be two distinct solutions of the differential equation \mathrm{ \frac{d y}{d x}=x+y,} with \mathrm{y_{1}(0)=0}and\mathrm{y_{2}(0)=1} respectively. Then, the number of points of intersection of  \mathrm{y=y_{1}(x)} and \mathrm{y=y_{2}(x)} is

Option: 1

0


Option: 2

1


Option: 3

2


Option: 4

3


Answers (1)

best_answer

\mathrm{\frac{d y}{d x}=x+y \Rightarrow \frac{d y}{d x}-y=x}

\mathrm{If =e^{-x}}

\mathrm{\therefore solution\; is\; y \cdot e^{-x}=\int x \cdot e^{-x} d x}

\mathrm{\Rightarrow y e^{-x}=-x e^{-x}-e^{-x}+c} \\

\mathrm{\Rightarrow y=-x-1+c e^{x}} \\

\mathrm{y_{1}(0)=0 \Rightarrow c=1} \\

\mathrm{\therefore y_{1}=-x-1+e^{x}}      ............(1)

\mathrm{y_{2}(0)=1 \Rightarrow c=2} \\

\mathrm{\therefore y_{2}=-x-1+2 e^{x} \ldots \text { (2) }} \\

\mathrm{\text { Now } y_{2}-y_{1}=e^{x}>0 \quad \therefore y_{2} \neq y_{1}}

\therefore Number of point of intersections of \mathrm{y_{1}\& \; y_{2}} is zero.

Hence correct option is 1

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