Home
Class 11
MATHS
If the line x-1=0 is the directrix of th...

If 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 (a)`1/8` (b) 8 (c) 4 (d) `1/4`

A

`1//8`

B

8

C

4

D

43469

Text Solution

Verified by Experts

The correct Answer is:
C
The equation of the directrix of this parabola is
`x-8/k=-k/4" "["Using:"x=-a]`
`rArr" "x=8/k-k/4`
But, the equation of the directrix is given as x-1=0
`:." "8/k-k/4=1rArrk^(2)+4k-32=0rArrk=-8, 4.`
Promotional Banner

Topper's Solved these Questions

  • PARABOLA

    OBJECTIVE RD SHARMA ENGLISH|Exercise SECTION-I (SOLVED MCQs EXAMPLE)|1 Videos

  • PARABOLA

    OBJECTIVE RD SHARMA ENGLISH|Exercise Section II - Assertion Reason Type|7 Videos

  • PARABOLA

    OBJECTIVE RD SHARMA ENGLISH|Exercise Chapter Test|30 Videos

  • PAIR OF STRAIGHT LINES

    OBJECTIVE RD SHARMA ENGLISH|Exercise Chapter Test|18 Videos

  • PERMUTATIONS AND COMBINATIONS

    OBJECTIVE RD SHARMA ENGLISH|Exercise Chapter Test|60 Videos

Similar Questions

Explore conceptually related problems

If 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 1/8 (b) 8 (c) 4 (d) 1/4

The directrix of the parabola x^2-4x-8y + 12=0 is

The directrix of the parabola x^2-4x-8y + 12=0 is

The directrix of the parabola x^2-4x-8y + 12=0 is

The equation of the directrix of the parabola x^(2) = 8y is

If the focus of the parabola x^2-k y+3=0 is (0,2), then a values of k is (are) (a) 4 (b) 6 (c) 3 (d) 2

If the focus of the parabola x^2-k y+3=0 is (0,2), then a values of k is (are) 4 (b) 6 (c) 3 (d) 2

The focus of the parabola y^(2)-4y-8x-4=0 is

If the line x-y+k =0 is a tangent to the parabola x^(2) = 4y then k = ?

If the line k^(2)(x-1)+k(y-2)+1=0 touches the parabola y^(2)-4x-4y+8=0 , then k can be

OBJECTIVE RD SHARMA ENGLISH-PARABOLA-Section I - Solved Mcqs
  1. The number of chords drawn from point (a, a) on the circle x^(2)+y"^(2...

    Text Solution

    |

  2. The length of the latusrectum of the parabola x=ay^(2)+by+c, is

    Text Solution

    |

  3. If the line x-1=0 is the directrix of the parabola y^2-k x+8=0 , then ...

    Text Solution

    |

  4. The number of parabolas that can be drawn , if two ends of the latus ...

    Text Solution

    |

  5. The number of points with integral coordinates that lie in the interio...

    Text Solution

    |

  6. Find the range of values of lamda for which the point (lamda,-1) is ex...

    Text Solution

    |

  7. A B is a chord of the parabola y^2=4a x with vertex AdotB C is drawn p...

    Text Solution

    |

  8. The coordinates of an end-point of the latusrectum of the parabola (y-...

    Text Solution

    |

  9. M is the foot of the perpendicular from a point P on a parabola y^2=4a...

    Text Solution

    |

  10. The equation of the parabola, whose vertex and focus are on the x-axis...

    Text Solution

    |

  11. If parabolas y^2=lambdax and 25[(x-3)^2+(y+2)^2]=(3x-4y-2)^2 are equal...

    Text Solution

    |

  12. The point on y^(2)=4ax nearest to the focus has to abscissa equal to

    Text Solution

    |

  13. The focal chord of the parabola y^2=a x is 2x-y-8=0 . Then find the eq...

    Text Solution

    |

  14. Number of common chords of a parabola & a circle can be

    Text Solution

    |

  15. A ray of light moving parallel to the x-axis gets reflected from parab...

    Text Solution

    |

  16. If y + b = m(1)(x + a) and y + b = m(2)(x+a) are two tangents to the p...

    Text Solution

    |

  17. If normals at the ends of the double ordinate x = 4 of parabola y^(2)=...

    Text Solution

    |

  18. Radius of the largest circle which passes through the focus of the par...

    Text Solution

    |

  19. If the tangents and normals at the extremities of a focal chord of a ...

    Text Solution

    |

  20. The axis of a parabola is along the line y = x and its vertex and focu...

    Text Solution

    |