IB Mathematics SL 1.7 Laws of exponents with rational exponents AA SL Paper 1- Exam Style Questions- New Syllabus
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
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: \( 2x + y \)