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Math Help - Functions

  1. #1
    Junior Member
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    Functions

    If f(x) =2x^3 + Ax^2 + 4x - 5 and f(2) = 5, what is the value of A?

    I keep getting = -31\2 but the correct answer is -7/2
    how do I get that? :| thank you
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by cokeclassic View Post
    If f(x) =2x^3 + Ax^2 + 4x - 5 and f(2) = 5, what is the value of A?

    I keep getting = -31\2 but the correct answer is -7/2
    how do I get that? :| thank you
    f(2) = 5 means

    2(2)^3 + A(2)^2 + 4(2) - 5 = 5

    \Rightarrow 16 + 4A + 8 - 5 = 5

    from here, simple arithmetic will get you the right answer (-7/2). want to try?
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  3. #3
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    Oh opps... I multiplied 2 x 2 first

    Thank you
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