Question

If the lines kx+3y+2 = 0, 3x-2y+9 = 0 are conjugate w.r.t.

y² = 4x, then k =

• A. 10
• B. 7/2
• C. –12
• D. –2

Answer 1

Answer: (D)

–2

Answer 2

If the lines l₁x+m₁y+n₁ =0, l₂x + m₂y + n₂ = 0 are conjugate lines w.r.to y² =4ax, then l₁n₂+l₂n₁ = 2am₁m₂.

**∴**K x 9 + 3 x 2 = 2 x 1 x 3 x – 2

⇒ K = -2.