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The normal at \mathrm{(a, 2 a)} meet the curve \mathrm{ y^2=4 a x} again at \mathrm{ \left(a t^2, 2 a t\right)} then the value of \mathrm{ t} equals
 

Option: 1

1


Option: 2

-1


Option: 3

-3


Option: 4

3


Answers (1)

best_answer

If the normal at \mathrm{\left(a t_1{ }^2, 2 a t_1\right)} w.r.t. parabola \mathrm{y^2=4 a x} meet the curve again at \mathrm{\left(a t_2{ }^2, 2 a t_2\right)} then we have
\mathrm{ t_2=-t_1-\frac{2}{t_1} }         ........(i)    
Here, we have \mathrm{a t_1{ }^2=a} and

\mathrm{ 2 a t_1=2 a \Rightarrow t_1=1 }

\mathrm{ For \: t_2 \: putting \: t_1=1\: in \: (i), we\: get }

\mathrm{ t_2=-1-\frac{2}{1}=-3 }

Hence option 3 is correct.


 

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manish painkra

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