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

Numerical solution of equations — practice question

(a)[2]

Show by sketching an appropriate pair of graphs that the equation $x^5 = 2 + x$ has one and only one real root.

(b)[2]

Show that, if the sequence defined by the iterative formula $$x_{n+1} = \frac{4x_n^5 + 2}{5x_n^4 - 1}$$ does converge, its limit is the root of the equation in part (a).

(c)[3]

Use the iterative formula, starting from $x_1 = 1.5$, to determine the root correct to $3$ decimal places. State each iterated value 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 a suitable graph, for example $y=x^5$

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