Exponential and logarithmic models

Practice sheet

Fresh questions from the whole chapter, to do on paper.

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  1. f(x)=24⋅4xf(x) = 24 \cdot 4^x. Find f(−1)f(-1).
  2. Is f(x)=4⋅(14)xf(x) = 4 \cdot \left(\tfrac{1}{ 4 }\right)^x exponential growth or decay?
    1. Decay: each step multiplies by 14\tfrac{1}{ 4 }
    2. Growth, because 4 is greater than 1
    3. A linear decrease
  3. The graph of an exponential function passes through (0,8)(0, 8) and (1,16)(1, 16). Write f(x)f(x).
  4. Evaluate log⁡416\log_{ 4 } 16.
  5. Solve 6x=216^x = 21. Write the exact answer using a logarithm.
  6. Match each logarithm statement with the same statement written as a power.
    1. log⁡8y=2\log_{ 8 } y = 2
    2. log⁡8y=3\log_{ 8 } y = 3
    3. log⁡8y=−1\log_{ 8 } y = -1
    4. log⁡8y=12\log_{ 8 } y = \tfrac{1}{2}
    1. y=82y = 8^{2}
    2. y=83y = 8^{3}
    3. y=18y = \dfrac{1}{ 8 }
    4. y=8y = \sqrt{ 8 }
  7. An account holds 400 dollars and grows continuously at 3% per year. Write the amount A(t)A(t) after tt years.
  8. The area of mold is f(t)=2e4tf(t) = 2e^{ 4t } square millimetres after tt days. By what factor is the area multiplied each day? Give the exact value.
  9. The graph of y=log⁡bxy = \log_b x passes through the point (9,2)(9, 2). What is bb?
  10. Where does the graph of y=ln⁡(x−3)y = \ln(x - 3) cross the xx-axis? Give the value of xx.
  11. What is the domain of y=ln⁡(x−6)y = \ln(x - 6)? Give it as an interval.
  12. Here is the graph of y=log⁡3(x−5)y = \log_{ 3 }(x - 5). Tap the point where it crosses the xx-axis.