Engineering
Mathematics
Section Formulae and Centres of a Triangle
Tangent of Parabola
Question

Let L1, L2 be the lines passing through the point P(0, 1) and touching the parabola 9x2 + 12x + 18y – 14 = 0. Let Q and R be the points on the lines L1 and L2 such that the ΔPQR is an isosceles triangle with base QR. If the slopes of the lines QR are m1 and m2, then 16(m12+m22) is equal to____.

JEE Advance
College PredictorLive

Know your College Admission Chances Based on your Rank/Percentile, Category and Home State.

Get your JEE Main Personalised Report with Top Predicted Colleges in JoSA

Solution

(3x + 2)2 = – 18y + 14 + 4

x+232=2(y1)

Let tangent be y = mx + 1

then x+232=2(mx+11)

x2+x43+2m+49=0

tangent D = 0

43+2m2169=0

m=043

tangent one y = 1

and y=4x3+1

Now slope of QR

are slope of angle bisectors of tangents

4x+3y35=±y11

Slopes m1 = 2

and m2=12

So, 16m12+m22

=164+14=68