From figure, x12+y12−12x1−16y1=300 (x1−6)2+(y1−8)2=400 …… (I) As, line AB in a chord of contact of the circle with respect topoint P(x1,y1), so xx1+yy1−6(x+x1)−8(y+y1)=0 x(x1−6)+y(y1−8)−(6x1+8y1)=0
x1−6
−5
=
y1−8
5
=
6x1+8y1
K
=λ So, x1=6−5λ, and y1=8+5λ …… (II) Form equation (I) and (II), we get 25λ2+25λ2=400 λ=±2√2 Also, λ=