EAMCET Engineering 2008 Solved Paper

Using the condition that if two lines l1x+m1y+n1=0 and l2x+m2y+n2=0 are conjugate w.r.t. parabola y2=4ax, then
l1n2+l2n1=2am1m2 . . . (i)
Given conjugate lines are 2x+3y+12=0
and x−y+4λ=0 and equation of parabola is y2=8x.
Here, l1=2,m1=3,n1=12;l2=1,m2=−1, n2=4λ and a=2
∴ From Eq. (i),
2×4λ+1×12=2×2×3×(−1)
8λ=−12−12⇒λ=−3