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Prove that , the normal to y2 = 12 x at (3,6) at meets the parabola again in (27,-18) & circle on this normal chord as diameter is x2+y2-30x+12y-27 = 0
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Sol. So here the parabola is y2=12x
If we compare with y2=4ax then we get, a=3
Then, parametric form of a point on the parabola is (at2,2at)
Here (3,6) is on parabola.
so, 2at = 6 t = 6/2a = 6/2 x3 = 6/6 = 1
then the equation of normal,
y+tx=2at+at3
y+x=6+3 y=9-x
If we put this value of y in parabola
(9-x)2=12x
81-18x+x2=12x
x2-18x+81-12x=0
x2-30x+81=0
x2-27x-3x+81=0
x(x-27)-3(x-27)=0
(x-27)(x-3)=0 x=3,27
We know already (3,6) is on the normal.
So, x = 27 Then, y = 9-x = 9 - 27 = -18
Then (27,-18) is also another intersection point with parabola.
Circle with normal chord as diameter
x2-30x+225+y2+12y+36-288=0
x2+y2-30x+12y-27=0, proved
Final Answer:
Hence it is proved that, Prove that , the normal to y2=12x at (3,6) meets the parabola again in (27,-18) & circle on this normal chord as diameter is x2+y2-30x+12y-27=0.
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