Home / IB Mathematics SL 1.7 Laws of exponents with rational exponents AA SL Paper 1- Exam Style Questions

IB Mathematics SL 1.7 Laws of exponents with rational exponents AA SL Paper 1- Exam Style Questions

IB Mathematics SL 1.7 Laws of exponents with rational exponents AA SL Paper 1- Exam Style Questions- New Syllabus

Question

Let \( x = \ln 3 \) and \( y = \ln 5 \). Write the following expressions in terms of \( x \) and \( y \).

Part (a):
\( \ln \left( \frac{5}{3} \right) \). [2 marks]

Part (b):
\( \ln 45 \). [4 marks]

▶️ Answer/Explanation
Detailed Solutions

Part (a) [2 marks]

Use the logarithm property: \( \ln \left( \frac{a}{b} \right) = \ln a – \ln b \).

\[ \ln \left( \frac{5}{3} \right) = \ln 5 – \ln 3 \]

Given: \( x = \ln 3 \), \( y = \ln 5 \).

\[ \ln 5 – \ln 3 = y – x \]

Answer: \( y – x \)

Part (b) [4 marks]

Recognize factors of 45: \( 45 = 9 \times 5 = 3^2 \times 5 \).

Use logarithm properties: \( \ln (ab) = \ln a + \ln b \), \( \ln (a^b) = b \ln a \).

\[ \ln 45 = \ln (3^2 \times 5) = \ln (3^2) + \ln 5 \]

\[ \ln (3^2) = 2 \ln 3 \]

\[ \ln 45 = 2 \ln 3 + \ln 5 \]

Substitute: \( \ln 3 = x \), \( \ln 5 = y \).

\[ \ln 45 = 2x + y \]

Answer: \( 2x + y \)

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