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Logarithmic Functions: math test solutions, Grade 11 – download the PDF

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Test solutions Grade 11 : Logarithmic Functions — Zyro the alien explorer of Planète Maths

Test solutions with the detailed point scale. Add up your points and spot what to review.

Suggested time: 45 minutes. Out of 20 points. Calculator allowed only when the problem says so.

2 Properties of logarithms / 3 pts

  1. \(\log_3 27+2\log_3 x-\log_3 y=3+2\log_3 x-\log_3 y\). (2 pts)
  2. \(\ln 8+\ln 5-\ln 10=\ln\dfrac{40}{10}=\ln 4\). (1 pt)

3 Exponential equations / 3 pts

  1. \(216=6^3\), so \(x-2=3\) and \(x=5\). (1 pt)
  2. \(5^x=20\) (1 pt), so \(x=\dfrac{\ln 20}{\ln 5}\approx 1.861\). (1 pt)

4 Logarithmic equations / 4 pts

  1. \(3x-2=4^3=64\) (1 pt), so \(x=22\). (1 pt)
  2. \(x(x+6)=16\), so \(x^2+6x-16=0\) (1 pt), i.e. \((x+8)(x-2)=0\). \(x=-8\) is rejected since the logs would be undefined; the solution is \(x=2\) (check: \(\log_2 2+\log_2 8=1+3=4\)). (1 pt)

5 Reading a graph / 3 pts

  1. Domain \(x\gt 1\); vertical asymptote \(x=1\). (1 pt)
  2. A\((2,2)\), B\((4,3)\), C\((10,4)\). Check: \(f(4)=\log_3 3+2=3\) and \(f(10)=\log_3 9+2=4\). (1 pt)
  3. \(f(28)=\log_3 27+2=3+2=5\). (1 pt)

6 Acidity of solutions / 3 pts

  1. \(\text{pH}=-\log(0.0025)\approx 2.60\). (1.5 pts)
  2. \([\text{H}^+]=10^{-8.3}\approx 5.0\times10^{-9}\) mol/L. (1.5 pts)
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