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

Numerical solution of equations — practice question

(i)[2]

By drawing a suitable pair of graphs, demonstrate that the equation $\ln x = 2 - x^2$ has only one root.

(ii)[2]

Use calculation to verify that this root lies between $x = 1.3$ and $x = 1.4$.

(iii)[1]

Show that, if a sequence produced by the iterative formula $x_{n+1} = \sqrt{2 - \ln x_n}$ converges, then its limit is the root of the equation in part (i).

(iv)[3]

Use the iterative formula $x_{n+1} = \sqrt{2 - \ln x_n}$ to find the root correct to $2$ decimal places. Record each iterate to $4$ decimal places.

Worked solution & mark scheme

This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: Produce a recognisable sketch of one appropriate graph, for example $y=\ln x$ or $y=2-x^2$

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