Question

The line $y = 2x + c$ is. a tangent to the parabola $y^2 = 16x$, if c equals

• A. -2
• B. 1
• C. 0
• D. 2

Answer 1

Answer: (D)

2

Answer 2

$y=mx+c$ touches $y^{2}=4ax$ if $c=\frac{a}{m}$ Here $m=2, a=16$ $\Rightarrow a=4$ $\therefore c=\frac{4}{2} = 2$