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Math Help - Exponential Functions Question

  1. #1
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    Exponential Functions Question

    Hi there, I'm trying to do this question but I'm stuck:

    Graph the function:
    f(x) = (2/3)x, -4
    ≤x≤1, x∈R

    f(-2) lies in the range [1, a]. If a
    ∈ N, then what is the minimum value of a?

    I've drawn the graph, but I don't understand the second part of the question. Could someone please help me?






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  2. #2
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    Re: Exponential Functions Question

    Quote Originally Posted by HelenMc9 View Post
    Graph the function:
    f(x) = (2/3)x, -4≤x≤1, x∈R
    f(-2) lies in the range [1, a]. If a ∈ N, then what is the minimum value of a?
    I've drawn the graph, but I don't understand the second part of the question. Could someone please help me?
    a = \left\lceil {f( - 2)} \right\rceil , that is ceiling function.
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  3. #3
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    Re: Exponential Functions Question

    You are asked to find the smallest natural number a such that f(-2) ≤ a.
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  4. #4
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    Re: Exponential Functions Question

    Sorry I don't get it, I'm still really confused ...
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  5. #5
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    Re: Exponential Functions Question

    Quote Originally Posted by HelenMc9 View Post
    Sorry I don't get it, I'm still really confused ...

    What does f(-2)=~?
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  6. #6
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    Re: Exponential Functions Question

    2.25?
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  7. #7
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    Re: Exponential Functions Question

    Quote Originally Posted by HelenMc9 View Post
    2.25?

    OK what is the smallest a\in\mathbb{N} so that f(-2)\in[1,a]~?
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  8. #8
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    Re: Exponential Functions Question

    Eh ... I don't know. What does ' f(-2) ∈ [1,a] ' mean? :/
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  9. #9
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    Re: Exponential Functions Question

    Quote Originally Posted by HelenMc9 View Post
    Eh ... I don't know. What does ' f(-2) ∈ [1,a] ' mean? :/

    You cannot do these questions if you don't know the basics

    It means 1\le f(-2)\le a.
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