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

Numerical solution of equations — practice question

(i)[2]

By drawing a suitable pair of graphs, show that the equation $x^3 = 3 - x$ has one and only one real root.

(ii)[2]

Show that, if a sequence of real values defined by the iterative formula $x_{n+1} = \frac{2x_n^3 + 3}{3x_n^2 + 1}$ converges, then its limit is the root of the equation in part (i).

(iii)[3]

Use this iterative formula to determine the root correct to 3 decimal places. Give the result of each iteration to 5 decimal places.

Worked solution & mark scheme

This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: Sketch an appropriate graph, for example $y=x^3$

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