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

Numerical solution of equations — practice question

(i)[2]

By drawing appropriate graphs, show that the equation $e^{2x} = 6 + e^{-x}$ has exactly one real root.

(ii)[2]

Check by calculation that this root is between $0.5$ and $1$.

(iii)[2]

Show that, if a sequence defined by the iterative formula $x_{n+1} = \frac{1}{3}\ln(1 + 6e^{x_n})$ converges, then its limit is the root of the equation in part (i).

(iv)[3]

Use the iterative formula to find the root correct to $3$ decimal places. Show each iteration to $5$ decimal places.

(c(iii))[2]

Show that if a sequence of values defined by the iterative formula $x_{n+1} = \frac{1}{3}\ln\left(1 + 6e^{x_n}\right)$ converges, then its limit is the root of the equation in part (i).

(c(iv))[3]

Use the iterative formula to calculate the root correct to 3 decimal places. Show the outcome of each iteration to 5 decimal places.

Worked solution & mark scheme

This 14-mark question has a full step-by-step worked solution and mark scheme. One marking point: Draw a suitable graph, for example $y=e^{2x}$

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