Solve exponential equation using logarithms

A question is this type if and only if it requires solving an exponential equation by taking logarithms of both sides, without substitution.

11 questions · Moderate -0.5

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CAIE P3 2009 November Q2
4 marks Moderate -0.8
2 Solve the equation \(3 ^ { x + 2 } = 3 ^ { x } + 3 ^ { 2 }\), giving your answer correct to 3 significant figures.
CAIE P3 2012 November Q2
4 marks Standard +0.3
2 Solve the equation $$5 ^ { x - 1 } = 5 ^ { x } - 5$$ giving your answer correct to 3 significant figures.
CAIE P3 2021 November Q1
4 marks Moderate -0.8
1 Find the value of \(x\) for which \(3 \left( 2 ^ { 1 - x } \right) = 7 ^ { x }\). Give your answer in the form \(\frac { \ln a } { \ln b }\), where \(a\) and \(b\) are integers.
CAIE P3 2021 November Q3
4 marks Moderate -0.3
3 Solve the equation \(4 ^ { x - 2 } = 4 ^ { x } - 4 ^ { 2 }\), giving your answer correct to 3 decimal places.
CAIE P3 2022 November Q3
4 marks Moderate -0.3
3 Solve the equation \(2 ^ { 3 x - 1 } = 5 \left( 3 ^ { - x } \right)\). Give your answer in the form \(\frac { \ln a } { \ln b }\), where \(a\) and \(b\) are integers.
CAIE P3 2022 November Q1
4 marks Moderate -0.5
1 Solve the equation \(2 ^ { 3 x - 1 } = 5 \left( 3 ^ { 1 - x } \right)\). Give your answer in the form \(\frac { \ln a } { \ln b }\) where \(a\) and \(b\) are integers.
CAIE P3 2024 November Q4
3 marks Standard +0.3
4 Solve the equation \(5 ^ { x } = 5 ^ { x + 2 } - 10\). Give your answer correct to 3 decimal places.
Edexcel C1 2013 June Q5
5 marks Easy -1.2
5. Solve
  1. \(2 ^ { y } = 8\)
  2. \(2 ^ { x } \times 4 ^ { x + 1 } = 8\)
OCR MEI C2 2005 June Q6
5 marks Moderate -0.8
6 Sketch the graph of \(y = 2 ^ { x }\).
Solve the equation \(2 ^ { x } = 50\), giving your answer correct to 2 decimal places.
OCR MEI C2 2007 June Q7
5 marks Easy -1.2
7
  1. Sketch the graph of \(y = 3 ^ { x }\).
  2. Use logarithms to solve the equation \(3 ^ { x } = 20\). Give your answer correct to 2 decimal places.
AQA C2 2006 June Q6
13 marks Moderate -0.3
6 The diagram shows a sketch of the curve with equation \(y = 27 - 3 ^ { x }\). \includegraphics[max width=\textwidth, alt={}, center]{f066f68a-e739-4da3-8ec1-e221461146b0-4_933_1074_376_484} The curve \(y = 27 - 3 ^ { x }\) intersects the \(y\)-axis at the point \(A\) and the \(x\)-axis at the point \(B\).
    1. Find the \(y\)-coordinate of point \(A\).
    2. Verify that the \(x\)-coordinate of point \(B\) is 3 .
  1. The region, \(R\), bounded by the curve \(y = 27 - 3 ^ { x }\) and the coordinate axes is shaded. Use the trapezium rule with four ordinates (three strips) to find an approximate value for the area of \(R\).
    1. Use logarithms to solve the equation \(3 ^ { x } = 13\), giving your answer to four decimal places.
    2. The line \(y = k\) intersects the curve \(y = 27 - 3 ^ { x }\) at the point where \(3 ^ { x } = 13\). Find the value of \(k\).
    1. Describe the single geometrical transformation by which the curve with equation \(y = - 3 ^ { x }\) can be obtained from the curve \(y = 27 - 3 ^ { x }\).
    2. Sketch the curve \(y = - 3 ^ { x }\).