Mathematics 9709 · AS & A Level · Numerical solution of equations

Numerical solution of equations — practice question

Work with the equation $\ln(x + 2) = 4e^{-x}$.
(i)[2]

By sketching an appropriate pair of graphs, demonstrate that the equation $\ln(x + 2) = 4e^{-x}$ has exactly one real root.

(ii)[2]

Use calculation to show that this root lies between $x = 1$ and $x = 1.5$.

(iii)[3]

Apply the iterative formula $x_{n+1} = \ln\!\left(\dfrac{4}{\ln(x_n + 2)}\right)$ to find the root correct to 2 decimal places. State every iteration result to 4 decimal places.

Worked solution & mark scheme

This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: Draw a suitable graph, for example $y=\ln(x+2)$

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