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Math Help - function of x

  1. #1
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    function of x

    you are given that f(x)=x^3+kx+c the value of f(0) is 6, and  x - 2 is a factor of f(x)

    Find the values of k and c

    ok i dont understand these at all, probably the last thing i have to revise and its my worst enemy. can someone explain??? thank yoouu
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  2. #2
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    Quote Originally Posted by RubbishAtMaths View Post
    you are given that f(x)=x^3+kx+c the value of f(0) is 6, and  x - 2 is a factor of f(x)

    Find the values of k and c

    ok i dont understand these at all, probably the last thing i have to revise and its my worst enemy. can someone explain??? thank yoouu
    Hello Rubbish,

    f(x)=x^3+kx+c

    f(0)=6 \Longrightarrow 0^3+k(0)+c=6 \Longrightarrow \boxed{c=6}

    If x-2 is a factor of f(x)=x^3+kx+c, then f(2)=0

    f(2)=0 \Longrightarrow 2^3+2k+6=0 \Longrightarrow \boxed{k=-7}
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  3. #3
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    muchly obliged govener, think i get em now
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