CAIE P3 2012 November — Question 1 3 marks

Exam BoardCAIE
ModuleP3 (Pure Mathematics 3)
Year2012
SessionNovember
Marks3
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicLaws of Logarithms
TypeSolve ln equation using subtraction law
DifficultyModerate -0.5 This is a straightforward application of the logarithm subtraction law (ln a - ln b = ln(a/b)) followed by exponentiating both sides. It requires only two standard steps with no conceptual difficulty, making it slightly easier than average but not trivial since students must recognize the structure and manipulate correctly.
Spec1.06f Laws of logarithms: addition, subtraction, power rules1.06g Equations with exponentials: solve a^x = b

1 Solve the equation $$\ln ( x + 5 ) = 1 + \ln x$$ giving your answer in terms of e.

Question 1:
AnswerMarks Guidance
Answer/WorkingMark Guidance
State or imply \(\ln e = 1\)B1
Apply at least one logarithm law for product or quotient correctly (or exponential equivalent)M1
Obtain \(x + 5 = ex\) or equivalent and hence \(\frac{5}{e-1}\)A1 [3]
## Question 1:

| Answer/Working | Mark | Guidance |
|---|---|---|
| State or imply $\ln e = 1$ | B1 | |
| Apply at least one logarithm law for product or quotient correctly (or exponential equivalent) | M1 | |
| Obtain $x + 5 = ex$ or equivalent and hence $\frac{5}{e-1}$ | A1 | [3] |

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1 Solve the equation

$$\ln ( x + 5 ) = 1 + \ln x$$

giving your answer in terms of e.

\hfill \mbox{\textit{CAIE P3 2012 Q1 [3]}}