If the line x-1 is the directrix of the parabola y2-k x-8-0 then positive value of k isA- 1 - 4B- 8C- 1 - 8D- 4

The correct option is D 4 Equation of parabola isy^2=k (x 8/k )⇒(y 0)^2=k (x 8/k ) ∴Equation of directrix is x 8/k= k/4⇒x=8/k k/4 But given x = 1 is directrix ...

You visited us 1 times! Enjoying our articles? Unlock Full Access!

Byju's Answer

Standard XII

Mathematics

General Equation of Parabola

If the line x...

Question

If the line x = 1 is the directrix of the parabola y² – kx + 8 = 0 then positive value of k is _______

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses

(1/4)

No worries! We‘ve got your back. Try BYJU‘S free classes today!

(1/8)

No worries! We‘ve got your back. Try BYJU‘S free classes today!

Open in App

Solution

The correct option is A
4

$Equation of parabola is y^{2} = k (x - \frac{8}{k}) \Rightarrow (y - 0)^{2} = k (x - \frac{8}{k}) ∴ Equation of directrix is x - \frac{8}{k} = \frac{- k}{4} \Rightarrow x = \frac{8}{k} - \frac{k}{4} But given x = 1 is directrix \Rightarrow 1 = \frac{8}{k} - \frac{k}{4} \Rightarrow k = - 8, 4$

Suggest Corrections

Similar questions

The line x-1=0 is the directrix of the parabola $y^{2} - k x + 8 = 0$ . Then one of the values of k is

Q. If the line

x - 1 = 0

is the directrix of the parabola

y^{2} - k x + 8 = 0,

then

k

can be

Q. If the line

x - 1 = 0

is the directrix of the parabola

y^{2} - k x + 8 = 0,

then values of

k

are

Q. If the line

x + 1 = 0

is the directrix of parabola

y^{2} - k x + 8 = 0

, then one of the value of

k

Q. The line

x - 1 = 0

is the directrix of the parabola

y^{2} - k x + 8 = 0.

Then one of the values of

k

Join BYJU'S Learning Program

If the line x = 1 is the directrix of the parabola y2 – kx + 8 = 0 then positive value of k is _______

The correct option is A 4 Equation of parabola isy2=k(x−8k)⇒(y−0)2=k(x−8k)∴Equation of directrix is x−8k=−k4⇒x=8k−k4But given x = 1 is directrix ⇒1=8k−k4⇒k=−8,4

If the line x = 1 is the directrix of the parabola y² – kx + 8 = 0 then positive value of k is _______