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Math Help - help algebra 2 functions

  1. #1
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    help algebra 2 functions

    f(x) 2x+1, g(x)=2x^2+x

    determine (gf)(3)

    ok so i dont know where to go since this is an online class

    g(f(3)?
    g(2(3)+1 = 7?
    g(7)?
    so confused someone please do this step by step i especially dont know how to do these when there are exponents like the 2x^2
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  2. #2
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    Quote Originally Posted by siberianfog View Post
    f(x) 2x+1, g(x)=2x^2+x

    determine (gf)(3)

    ok so i dont know where to go since this is an online class

    g(f(3)?
    g(2(3)+1 = 7?
    g(7)?
    so confused someone please do this step by step i especially dont know how to do these when there are exponents like the 2x^2
    g[f(3)] = g[2(3)+1] = g(7) = 2(7)^2 + 7 = 2(49) + 7 = 98 + 7 = 105
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  3. #3
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    wow thank you i have been getting them done fast now, 1 more pleasE? its very very very appreciated.

    f(x) 2x+1, g(x)=2x^2+x
    determine (fg)(x+1)
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  4. #4
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    Quote Originally Posted by siberianfog View Post
    wow thank you i have been getting them done fast now, 1 more pleasE? its very very very appreciated.

    f(x) 2x+1, g(x)=2x^2+x
    determine (fg)(x+1)
    f[g(x+1)] = f[2(x+1)^2+(x+1)] = ... you finish it.
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  5. #5
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    2(x^2+1)+(x+1)
    2x^2+2+x+1
    2x^2+3+x

    I GOT
    2(2x^2 + 3 + x) = 4x^2 + 6 + x

    but the book says thats wrong

    4x^2+10x+7? dont know where you get that
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  6. #6
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    2(x^2+1)+(x+1)
    ... note that (x+1)^2 \ne x^2+1
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  7. #7
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    where do i go wrong?

    2(x^2 + 1) + (x+1)
    2x^2 + 2 + x + 1
    2x^2 + 3 + x

    2(2x^2 + 3x + x)
    4x^2 + 6x + 2x + 1
    4x^2 + 8x + 1
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  8. #8
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    once again ... 2(x+1)^2 + (x+1) \ne 2(x^2+1) + (x+1)

    specifically ... (x+1)^2 does not equal (x^2+1)


    I recommend you research how to square a binomial.
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  9. #9
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    Thank you
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