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    f(x) R is [3 + k, ∞)

    g(x) R is [-2, ∞)

    that's what i got so far, i'm stuck on part b) because i'm quite confused about domain of composite functions...what is the domain of gf(x)?
    i know i need to make an equation with 3+k but im not sure what it should be equal to
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    (Original post by ihatePE)
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    f(x) R is [3 + k, ∞)

    g(x) R is [-2, ∞)

    that's what i got so far, i'm stuck on part b) because i'm quite confused about domain of composite functions...what is the domain of gf(x)?
    i know i need to make an equation with 3+k but im not sure what it should be equal to
    Firstly, your range of g(x) is incorrect, you should be able to see this if you plot the graph.
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    (Original post by NotNotBatman)
    Firstly, your range of g(x) is incorrect, you should be able to see this if you plot the graph.
    oops, i've worked it out again and i came to [0, ∞)
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    (Original post by ihatePE)
    oops, i've worked it out again and i came to [0, ∞)
    What are the coordinates of the minimum point of g(x) = x^2-6? Is this the minimum point when the domain is restricted to x>-2 ?

    Remember when finding the range, you have to consider the values that the function g output, that is the y values of the function, not the input ( x values).
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    (Original post by NotNotBatman)
    What are the coordinates of the minimum point of g(x) = x^2-6? Is this the minimum point when the domain is restricted to x>-2 ?

    Remember when finding the range, you have to consider the values that the function g output, that is the y values of the function, not the input ( x values).
    ooooo is it [-6, ∞)?
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    (Original post by ihatePE)
    ooooo is it [-6, ∞)?
    Yes.

    Now part(b), the function gf can be formed if the range of f is contained within (is a subset of) or equal to the domain of g. You've already worked out the range of g as 3+k. Now work out the least k for the range of the function f under the same restricted domain to be contained within the domain of g.
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    (Original post by NotNotBatman)
    Yes.

    Now part(b), the function gf can be formed if the range of f is contained within (is a subset of) or equal to the domain of g. You've already worked out the range of g as 3+k. Now work out the least k for the range of the function f under the same restricted domain to be contained within the domain of g.
    i have 3 + k ≥ -2
    therefore k ≥ -5
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    (Original post by ihatePE)
    i have 3 + k ≥ -2
    therefore k ≥ -5
    That should be correct.
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    (Original post by NotNotBatman)
    That should be correct.
    thanksss, composites r so complicated urghhh
 
 
 
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