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    Given that the equation kx^2+12x+k=0, where k is a positive constant, has equal roots, find the value of k.

    (4 marks)

    Any useful hints? I prefer them to actual solutions! (but feel free)

    Cheers
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    discriminant = 0 for equal roots
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    this thread is a duplicate... so i'm sorry to say that it's been answered already...
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    k, i gotta question relating to this. suppose u got x^2 + bx + c = 0, and the roots of the are (1 + sqrt 5) and (1 - sqrt 5)
    how would u go about answering this? like wat do u have to do, an explanation will do just fine.
    thanx

    edit: sorry didn't write out teh complete question, yeah so u have to find out the value of b and c!
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    roots are:
    [-b ± sqrt[b² - 4ac] ] / 2a
    so as roots are 1±sqrt5
    then
    1±sqrt5 = [-b ± sqrt[b² - 4ac] ] / 2a
    a is 1 ( as it's x²)
    so:
    1±sqrt5 = [-b ± sqrt[b² - 4c] ] / 2
    so 1 = -b/2
    b = -2

    and 1/2 sqrt [ b² - 4c] = sqrt 5
    sqrt[b²/4 - 4/4 c] = sqrt 5
    sqrt[(-2)²/4 - 4/4 c] = sqrt 5
    sqrt[1 - c] = sqrt 5
    so:
    1-c = 5
    c = -4
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    (Original post by Lawbutwhere?)
    Given that the equation kx^2+12x+k=0, where k is a positive constant, has equal roots, find the value of k.

    (4 marks)

    Any useful hints? I prefer them to actual solutions! (but feel free)

    Cheers

    Equal roots mean that the discriminant = 0

    b^2 - 4ac is the discriminant. I will give you no more clues, hope this helps.
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    lol...


    this thread is a duplicate... so i'm sorry to say that it's been answered already...
    no need to give more clues!
 
 
 
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