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    How do i do 13 iii) - i don't get it :/
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    write

    x4 - 2 = kx2

    investigate the Discriminant... this tells you how many roots the equation has.
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    (Original post by the bear)
    write

    x4 - 2 = kx2

    investigate the Discriminant... this tells you how many roots the equation has.
    Discriminant = b^2 - 4ac

    ....Stuck. What do i do with the x^4?
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    (Original post by tmifan)
    Discriminant = b^2 - 4ac

    ....Stuck. What do i do with the x^4?
    this is a disguised quadratic...
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    (Original post by the bear)
    this is a disguised quadratic...
    So its just:
    (-k)^2 - (4 x 1 x -2)

    = -k^2 + 8

    Then?
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    (Original post by tmifan)
    So its just:
    (-k)^2 - (4 x 1 x -2)

    = -k^2 + 8

    Then?
    discriminant = k2 + 8

    what does that tell you ?
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    (Original post by tmifan)
    So its just:
    (-k)^2 - (4 x 1 x -2)

    = -k^2 + 8

    Then?
    (-k)^2 = -k \times -k  = -1 \times k \times -1 \times k = -1 \times -1 \times k \times k = 1 \times k \times k = k^2.
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    (Original post by the bear)
    discriminant = k2 + 8

    what does that tell you ?
    ...I don't know...
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    (Original post by tmifan)
    ...I don't know...
    What does the discriminant always being greater than 0 mean?
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    (Original post by Zacken)
    What does the discriminant always being greater than 0 mean?
    2 roots!

    but how do you know its greater than 0...from k2 + 8
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    (Original post by tmifan)
    2 roots!

    but how do you know its greater than 0...from k2 + 8
    Well what do you know about a squared number? What do you get is you take a squared number and add a positive number?

    If you cannot answer that, then think about what is (-100)^2 - what is (-200)^2 - what is (1)^2, what do they all have in common?
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    (Original post by Zacken)
    Well what do you know about a squared number? What do you get is you take a squared number and add a positive number?

    If you cannot answer that, then think about what is (-100)^2 - what is (-200)^2 - what is (1)^2, what do they all have in common?
    Oh duhh! sorry that was a stupid question

    Okay i get it now! Thank you both!
 
 
 
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