The variables $x$ and $y$ are linked by $x = A(3^{-y})$, with $A$ as a constant.
(a)[3]
Explain why the graph of $y$ against $\ln x$ is a straight line, and state the exact gradient of the line.
(b)[2]
The line is stated to cross the $y$-axis at the point where $y = 1.3$. Calculate $A$, and give your answer correct to 2 decimal places.
Worked solution & mark scheme
This 5-mark question has a full step-by-step worked solution and mark scheme. One marking point: “State or imply that $\ln x=\ln A-y\ln 3$” …
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