Question
Question: If x+y+k = 0 is a tangent to the parabola x<sup>2</sup> = 4y, then k =...
If x+y+k = 0 is a tangent to the parabola x2 = 4y, then k =
A
1
B
2
C
-1
D
4
Answer
1
Explanation
Solution
If lx+my+n =0 is a tangent to the parabola x2 = 4ay, then al2 = mn.
∴ If x+y+k is a tangent to the parabola x2 = 4y then 1.12 = 1.K ⇒ K = 1.