Question

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57. Image of Q (2, 4) with respect to y-axis is Q? then distance between QQ' is
1) 4
2) 8
3) 6
4) 2
1)
2)
3)
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Answer 1

Answer:

Correct option is

A

x

2

+y

2

−20x+8y−12=0

Normal at (at

1

2

,2at

1

) meets the parabola again at (at

2

2

,2at

2

)

Then,

t

2

=−t

1

−

t

1

2

Given parabola is y

2

=8x

⇒a=2

P=(2,4)

⇒2at

1

=4

∴t

1

=1

⇒t

2

=−t

1

−

t

1

2

⇒t

2

=−3

Then, P=(2,4) and Q=(18,−12)

Then, equation of circle is given by

(x−2)(x−18)+(y−4)(y+12)=0

∴x

2

+y

2

−20x+8y−12=0