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Given f(x) = -log3 x, find the domain of f, the equation of f⁻¹, and the transformation from f⁻¹ to h(x) = 3^x - 5.

Mathematics

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Answers

2 parts
5.1

x>0\text{}x > 0\text{}

5.2

y=3−x\text{}y = 3^{-x}\text{}

Step-by-step solution

7 steps

Part 5

Sketched below is the graph of f(x)=−log⁡xf(x) = -\log x.

Part 5.1

x>0\text{}x > 0\text{}

Write down the domain of f.

  1. Identify the condition for the logarithm to be defined.

    For a logarithmic function log⁡x\log x to be defined, its argument xx must be strictly positive. The negative sign in front of log⁡x\log x does not affect the domain.
    The domain of ff is x>0\boxed{\text{}x > 0\text{}}

Part 5.2

y=3−x\text{}y = 3^{-x}\text{}

Write down the equation of f−1f^{-1} in the form y=…y = \dots.

  1. Assume a base for the logarithm.

    Given the context of part 5.3, where h(x)=3x−5h(x) = 3^x - 5, it is implied that the base of the logarithm is 3. So, f(x)=−log⁡3xf(x) = -\log_3 x.
    Let y=−log⁡3xy = -\log_3 x.

  2. Swap xx and yy.

    x=−log⁡3yx = -\log_3 y
  3. Solve for yy.

    Multiply both sides by −1-1:

    −x=log⁡3y-x = \log_3 y

    Convert the logarithmic equation to an exponential equation:

    y=3−xy = 3^{-x}

    The equation of f−1(x)f^{-1}(x) is y=3−x\boxed{\text{}y = 3^{-x}\text{}}

Part 5.3· 2 steps

Describe the transformation from f−1f^{-1} to hh if h(x)=3x−5h(x) = 3^x - 5.

  1. Identify f−1(x)f^{-1}(x).

    From 5.2, f−1(x)=3−xf^{-1}(x) = 3^{-x}.

  2. Compare f−1(x)f^{-1}(x) with h(x)h(x).

    We need to transform y=3−xy = 3^{-x} into y=3x−5y = 3^x - 5.
    First, to change 3−x3^{-x} to 3x3^x, we reflect the graph of y=3−xy = 3^{-x} about the y-axis (replace xx with −x-x). This gives y=3−(−x)=3xy = 3^{-(-x)} = 3^x.
    Next, to change 3x3^x to 3x−53^x - 5, we translate the graph of y=3xy = 3^x vertically downwards by 5 units.
    The transformation is a reflection about the y-axis followed by a vertical translation of 5 units downwards.

Part 5.4· 1 step

Use the graph of ff to solve for xx if k(x)k(x) is the reflection of ff about the x-axis and k(x)≥3k(x) \geq 3.

  1. Determine the equation of k(x)k(x).

    Given f(x)=−log⁡3xf(x) = -\log_3 x.
    A reflection about the x-axis

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