Question

If the parabola $y^{2}=4 ax$ passes through the point $(1,-2)$, then the tangent at this point is

• A. $x+y-1=0$
• B. $x-y-1=0$
• C. $x+y+1=0$
• D. $x-y + 1=0$

Answer 1

Answer: (C)

Since the parabola $y ^{2}=4 ax$ passes through the point
$(1,-2), \therefore (-2)^{2}=4 a(1) \Rightarrow a=1$
Equation of tangent to the parabola at $(1,-2)$ is
$y y_{1}=2 a\left(x+x_{1}\right)$ or $y(-2)=2(1)(x+1)$ or $x+y+1=0$