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    hey

    I came across this while doing some past papers, I am wondering that this function means
    f^2(x)
    for example f(x) = 2x so what would f^2(x)?
    I thought it means square the f(x) but that answer in the mark scheme isn't 4x^2

    thanks a lot
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    I think it means do the function twice, so f(f(x)) or fof. In this case, 2(2x)=4x. I'm not certain, though. Have you got the right answer in the mark scheme?

    It could just about mean second derivative of f, but that would be horribly non-standard notation.
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    (Original post by Tempeststurm)
    I think it means do the function twice, so f(f(x)) or fof. In this case, 2(2x)=4x. I'm not certain, though. Have you got the right answer in the mark scheme?

    It could just about mean second derivative of f, but that would be horribly non-standard notation.
    yep your right its 4x.

    just another question:

    a curve has the equation: y=(x+2)e^{-x} and a line  y=(x+2) crosses the curve

    There are two points of intersection 0 and -2
    I can't algebrically solve it to get -2 I keep getting 0.
    someone please help
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    well you just solve
    (x+2)e^-x=(x+2)
    that means that (x+2)[e^-x)-1]=0 substracting
    Therefore x+2=0 OR (e^-x)-1=0
    so x=-2 or e^-x=1, that is x=0
    that's it your error I think was to divide both sides by x+2...you cannot do this if x+2=0 so basically you loose a solution
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    (x+2)(e^-x -1)=0

    so e^-x -1 =0 or x+2 = 0

    so x = 0 or -2
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    (Original post by paronomase)
    well you just solve
    (x+2)e^-x=(x+2)
    that means that (x+2)[e^-x)-1]=0 substracting
    Therefore x+2=0 OR (e^-x)-1=0
    so x=-2 or e^-x=1, that is x=0
    that's it your error I think was to divide both sides by x+2...you cannot do this if x+2=0 so basically you loose a solution
    sorry i don't get this part, how did you get this from both the equations...mind explaining this in detail?
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    (Original post by New Username)
    sorry i don't get this part, how did you get this from both the equations...mind explaining this in detail?

    taking out a factor of (x+1)
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    (Original post by Tallon)
    taking out a factor of (x+1)
    I was actually talking about the subtracting but I just got it now!
    Yeah I was dividing both sides by (x+2) which meant I was loosing one of the solutions. Thanks a lot for your help

    Thanks everyone!
 
 
 
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