badge image

Enroll For Free Now & Improve Your Performance.

User Icon
User Icon
User Icon
User Icon
User Icon

Thank you for registering.

One of our academic counsellors will contact you within 1 working day.

Please check your email for login details.

Use Coupon: CART20 and get 20% off on all online Study Material

Total Price: Rs.

There are no items in this cart.
Continue Shopping
Grade: 11


The value of k for which the line x+y+1=0 touches the parabola y^2=kx is

3 years ago

Answers : (3)

Saurabh Koranglekar
askIITians Faculty
8407 Points
6 months ago
Vikas TU
12281 Points
The line x+y=1 touches the parabola y^2=kx or y^2=4.k/4 x ( Compare with standard eqn y^2=4ax) so a= k/4 and the condition of tangency for the line y=mx+c  to a parabola y^2=4ax is that : c=a/m
we ghave given c=1,  m=-1, a=k/4 This implies 1=k/4(-1) => k=-4
6 months ago
24735 Points

x+y-1=0. or. y=1-x………(1)

y^2. = kx……………………..(2)

On putting y=1-x from eq.(1)


1–2x+x^2 =kx

x^2 - (k+2)x+1 = 0

The given line is tangent to the parabola which touches the parabola one and only one point. means both the roots are same.

D or. b^ - 4 a.c. =0

{-(k+2)}^2. - 4.1.1. =0

(k+2)^2. = 4

(k+2) = +/-(2)

k= -2 +/-2

k= -2+2 or. -2–2.

k =0. , - 4. Answer.

6 months ago
Think You Can Provide A Better Answer ?
Answer & Earn Cool Goodies

Course Features

  • 731 Video Lectures
  • Revision Notes
  • Previous Year Papers
  • Mind Map
  • Study Planner
  • NCERT Solutions
  • Discussion Forum
  • Test paper with Video Solution

Course Features

  • 53 Video Lectures
  • Revision Notes
  • Test paper with Video Solution
  • Mind Map
  • Study Planner
  • NCERT Solutions
  • Discussion Forum
  • Previous Year Exam Questions

Ask Experts

Have any Question? Ask Experts

Post Question

Answer ‘n’ Earn
Attractive Gift
To Win!!! Click Here for details