Feb/Mar 2023 p32 q1
1564
It is given that \(x = \ln(2y - 3) - \ln(y + 4)\).
Express \(y\) in terms of \(x\).
Solution
Start with the given equation:
\(x = \ln(2y - 3) - \ln(y + 4)\)
Use the logarithm property \(\ln a - \ln b = \ln \left( \frac{a}{b} \right)\):
\(x = \ln \left( \frac{2y - 3}{y + 4} \right)\)
Exponentiate both sides to remove the logarithm:
\(e^x = \frac{2y - 3}{y + 4}\)
Cross-multiply to solve for \(y\):
\(e^x (y + 4) = 2y - 3\)
Expand and rearrange terms:
\(e^x y + 4e^x = 2y - 3\)
\(2y - e^x y = 3 + 4e^x\)
Factor out \(y\):
\(y(2 - e^x) = 3 + 4e^x\)
Solve for \(y\):
\(y = \frac{3 + 4e^x}{2 - e^x}\)
Log in to record attempts.