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

Numerical solution of equations — practice question

The diagram presents the curve whose equation is $y = x^4 + 2x^3 + 2x^2 - 12x - 32$. The curve intersects the $x$-axis at the points with coordinates $(\alpha, 0)$ and $(\beta, 0)$.
(i)[2]

Use the factor theorem to show that, in fact, $(x + 2)$ is a factor of $x^4 + 2x^3 + 2x^2 - 12x - 32$.

(ii)[3]

Show that $\beta$ can be expressed in an equation of the form $x = \sqrt[3]{(p + qx)}$, and give the values of $p$ and $q$.

(iii)[3]

Use an iterative formula based on the equation in part (ii) to find $\beta$ correct to 4 significant figures. Record each iteration to 6 significant figures.

(c(ii))[3]

Show that $\beta$ matches an equation of the form $x = \sqrt[3]{(p + qx)}$, and give the values of $p$ and $q$.

(c(iii))[3]

Use an iterative formula based on the equation in part (ii) to find $\beta$ correct to $4$ significant figures. Record each iteration to $6$ significant figures.

Worked solution & mark scheme

This 14-mark question has a full step-by-step worked solution and mark scheme. One marking point: Substitute $x=-2$, then simplify the expression

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