"For a given parabola and a given point (h, k), this cubic in m has three roots say m1, m2, m3 i.e. from (h, k) three normals can be drawn to the parabola whose slopes are m1, m2, m3. For this cubic, we have m1 + m2 + m3 = 0, m1 m2 + m 2 m3 + m3 m1 = (2a – h)/a and m1 m2 m3 = –k/a."
Prove : 

1. ​m1 m2 + m2 m3 + m3 m1 = (2a – h)/a 

​2.​m1 m2 m3 = –k/a.

Dear Student,
Please find below the solution to the asked query:

We know that equation of normal of m-slope of parabola is y=mx-2am-am3Normal passes through h,kk=mh-2am-am3am3+m2a-h+k=0 Roots will be m1,m2,m3Hencem1+m2+m3=-Coeffcient of m2Coefficient of m3=0a=0m1m2+m2m3+m3m1=Coeffcient of mCoefficient of m3=2a-ham1m2m3=-Constant termCoefficient of m3=-ka

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