Question

If $x+y=k$ is a tangent to the parabola $y^2=12x,$ then k is equal to

• A. $9$
• B. $-9$
• C. $3$
• D. $-3$

Answer 1

Answer: (D)

If $x+y=k\Rightarrow y=-x+k$
is a tangent to the parabola
$y^2=12x,$
then $k=\frac{3}{-1}=-3$
$\left[\because c=\frac{a}{m}\right]$