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Math Help - In each case compute f o g (x) where

  1. #1
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    In each case compute f o g (x) where

    f(x) = 2x + 3 and g(x) = x^2 − 1.

    fog(x)= 2(x^2-1)+3
    gof(x) = 2x^2+1

    gof (x) dosent equal to fog(x)

    f(x) = x^2 − 1 and g(x) = 2x + 3.

    fog ( x) = x(2x+3)^2-1
    gof(x)= 4x^2+12x+8

    gof (x) dosent equal to fog(x)

    are thses right with proper working ?

    if not can some1 show me the answear and the proper working
    cheers
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  2. #2
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    Re: In each case compute f o g (x) where

    Quote Originally Posted by arsenal12345 View Post
    f(x) = 2x + 3 and g(x) = x^2 − 1.

    fog(x)= 2(x^2-1)+3
    gof(x) = 2x^2+1

    gof (x) dosent equal to fog(x)

    f(x) = x^2 − 1 and g(x) = 2x + 3.

    fog ( x) = x(2x+3)^2-1
    gof(x)= 4x^2+12x+8

    gof (x) dosent equal to fog(x)

    are thses right with proper working ?

    if not can some1 show me the answear and the proper working
    cheers
    In question 1, \displaystyle \begin{align*} f \circ g (x) \end{align*} is correct, \displaystyle \begin{align*} g \circ f(x) \end{align*} is not.
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  3. #3
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    Re: In each case compute f o g (x) where

    Quote Originally Posted by Prove It View Post
    In question 1, \displaystyle \begin{align*} f \circ g (x) \end{align*} is correct, \displaystyle \begin{align*} g \circ f(x) \end{align*} is not.
    is it 4x^3 + 9x+12 - 1 ??

    fog (x) dosent eqauel to gof (x)
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  4. #4
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    Re: In each case compute f o g (x) where

    Quote Originally Posted by arsenal12345 View Post
    is it 4x^3 + 9x+12 - 1 ??

    fog (x) dosent eqauel to gof (x)
    No.

    \displaystyle \begin{align*} g \circ f(x) &= g\left(f(x)\right) \\ &= \left(2x + 3\right)^2 - 1 \\ &= 4x^2 + 12x + 9 - 1 \\ &= 4x^2 + 12x + 8 \end{align*}
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