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Math

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1.Let f(x)= x^2 - 5 and g(x)= 3x^2. Find g(f(x)).
2. Let f(x)= x^2 - 4 and g(x) -3x^2. Find f(g(x)).

  • Math -

    g(x)= -3x^2
    g(f(x))= -3(x^2-4)^2
    -6(x^2-4)(2x)
    -6x^2-24 (2x)
    -12x^3-48x
    -12x(x^2+4)

    f(g(x))= (-3x^2)^2-4
    2(-3x^2)(-6x)-4
    -6x^2(-6x)-4
    36x^3-4
    4(9x^3-1)

  • Math -

    I think you're doing it wrong, because I am not getting those answers. I got answer choices.

  • Math -

    Neil -- for heaven's sakes! If you have answer choices, please post them along with your problem!

  • Math -

    1. Let f(x)= x^2 - 5 and g(x)= 3x^2. Find g(f(x)).
    A. 3x^4 - 30x^2 + 75
    B. -3x^4 - 15
    C. 9x^4
    D. -3x^4 - 4

    2. Let f(x)= x^2 - 4 and g(x)= -3x^2. Find f(g(x)).
    F. -3x^4 + 12
    G. -3x^4 + 24x^2 - 48
    H. 9x^4 - 4
    I. -3x^4 - 4

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