If the parabola y2=4 ax passes through the point (1,-2), then the tangent at this point is

Question

If the parabola y2=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

Tardigrade Admin · Accepted Answer

Since the parabola y 2=4 ax passes through the point (1,-2), ∴ (-2)2=4 a(1) ⇒ a=1 Equation of tangent to the parabola at (1,-2) is y y1=2 a(x+x1) or y(-2)=2(1)(x+1) or x+y+1=0

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

$x + y - 1 = 0$

$x - y - 1 = 0$

$x + y + 1 = 0$

$x - y + 1 = 0$

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

Q. If the parabola y2=4ax passes through the point (1,−2), then the tangent at this point is

x+y−1=0

x−y−1=0

x+y+1=0

x−y+1=0