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Math Help - Discriminant

  1. #1
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    Discriminant

    Determine the value(s) of k for which x2 + (k-2)x - 2k = 0 has equal and real roots.
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  2. #2
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    Hello, xxlvh!

    Determine the value(s) of k for which . x^2 + (k-2)x - 2k \:= \:0
    has equal and real roots.

    We're expected to know that a quadratic has equal roots if its discriminant is zero.
    . . That is: . b^2-4ac \:=\:0

    We have: . a \:= \:1,\;b \:= \:k-2,\;c \:= \:\text{-}2k

    Therefore: . (k-2)^2 - 4(1)(\text{-}2k) \:=\:0 . . . . now solve for k.

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  3. #3
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    seasons greetings. =)

    Okay, so I had had simplified it down to k2-12k+4 = 0 theen
    my final solution was k = 6, and -2.
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  4. #4
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by xxlvh View Post
    seasons greetings. =)

    Okay, so I had had simplified it down to k2-12k+4 = 0 theen
    my final solution was k = 6, and -2.
    that is wrong. you expanded Soroban's expression incorrectly

    (you can check your own solutions by plugging in the values you got for k and see if you get zero. you may want to plug them into Soroban's expression as a double check)
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