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If the normals to the parabola `y^2=4a x`at three points `(a p^2,2a p),`and `(a q^2,2a q)`are concurrent, then the common root of equations `P x^2+q x+r=0`and `a(b-c)x^2+b(c-a)x+c(a-b)=0`is`p`(b) `q`(c) `r`(d) `1`A. pB. qC. rD. 1

Answer» Correct Answer - D
(4) Normal at points `(ap^(2),2ap),(aq^(2),2aq),and(ar^(2),2ar)` are concurrent.
Hence, the points are co-normal points. Therefore,
p+qr=0
So, `px^(2)+qx+r=0` has one root which is x=1.
Therefore, the common root is 1, which also satisfies the second equation.


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