SPS SPS FM 2024 February — Question 10

Exam BoardSPS
ModuleSPS FM (SPS FM)
Year2024
SessionFebruary
TopicComplex Numbers Argand & Loci
TypeComplex arithmetic operations
DifficultyStandard +0.3 This is a standard A-level Further Maths question on finding complex roots using the quadratic formula. Part (a) requires straightforward application of the quadratic formula with complex arithmetic (discriminant is negative). Part (b) involves sketching standard loci (perpendicular bisector and circle) and finding intersections. These are routine techniques covered in FM complex numbers with no novel problem-solving required, making it slightly easier than average.
Spec1.02y Partial fractions: decompose rational functions4.03b Matrix operations: addition, multiplication, scalar4.03c Matrix multiplication: properties (associative, not commutative)4.03g Invariant points and lines4.03h Determinant 2x2: calculation4.03i Determinant: area scale factor and orientation4.04a Line equations: 2D and 3D, cartesian and vector forms4.04c Scalar product: calculate and use for angles4.04e Line intersections: parallel, skew, or intersecting4.08a Maclaurin series: find series for function4.08b Standard Maclaurin series: e^x, sin, cos, ln(1+x), (1+x)^n

$$\begin{aligned} & l _ { 1 } : \mathbf { r } = \left( \begin{array} { c } 10 \\ 3 \end{array} \right) + \lambda \left( \begin{array} { c } 2 \\ - 2 \\ 1 \end{array} \right) \\ & l _ { 2 } : \mathbf { r } = \left( \begin{array} { l } 5 \\ 2 \\ 4 \end{array} \right) + \mu \left( \begin{array} { c } 3 \\ 1 \\ - 2 \end{array} \right) \end{aligned}$$ \(P\) is the point of intersection of \(l _ { 1 }\) and \(l _ { 2 }\).
  1. Find the position vector of \(P\).
  2. Find, correct to 1 decimal place, the acute angle between \(l _ { 1 }\) and \(l _ { 2 }\). \(Q\) is a point on \(l1\) which is 12 metres away from \(P \cdot R\) is the point on \(l2\) such that \(QR\) is perpendicular to \(l1\).
  3. Determine the length \(QR\).
    [0pt]
    5. (a) Express \(\frac { 5 + 4 x - 3 x ^ { 2 } } { ( 1 - 2 x ) ( 2 + x ) ^ { 2 } }\) in three partial fractions.
    (b)
    Hence find the first three terms in the expansion of \(\frac { 5 + 4 x - 3 x ^ { 2 } } { ( 1 - 2 x ) ( 2 + x ) ^ { 2 } }\) in ascending powers of \(x\).
    (c) State the set of values for which the expansion in part (b) is valid.
    [0pt]
    6. The matrices \(\mathbf { A }\) and \(\mathbf { B }\) are given by \(\mathbf { A } = \left( \begin{array} { l l } 1 & a \\ 3 & 0 \end{array} \right)\) and \(\mathbf { B } = \left( \begin{array} { l l } 4 & 2 \\ 3 & 3 \end{array} \right)\).
    (a) Find the value of a such that \(\mathbf { A B } = \mathbf { B A }\).
    (b) Prove by counter example that matrix multiplication for \(2 \times 2\) matrices is not commutative.
    (c) A triangle of area 4 square units is transformed by the matrix \(\mathbf { B }\). Find the area of the image of the triangle following this transformation.
  4. Find the equations of the invariant lines of the form \(y = m x\) for the transformation represented by matrix \(\mathbf { B }\).
    [0pt]
    7. (a) In this question you must show detailed reasoning. Find the roots of the equation \(2 z ^ { 2 } - 2 z + 5 = 0\).
    (b) The loci \(C _ { 1 }\) and \(C _ { 2 }\) are given by \(| z | = | z - 2 i |\) and \(| z - 2 | = \sqrt { 5 }\) respectively.
    i. Sketch on a single Argand diagram the loci \(C _ { 1 }\) and \(C _ { 2 }\), showing any intercepts with the imaginary axis.
    ii. Indicate, by shading on your Argand diagram, the region \(\{ z : | z | \leqslant | z - 2 \mathrm { i } | \} \cap \{ z : | z - 2 | \leqslant \sqrt { 5 } \}\).
    (c) i. Show that both of the roots of the equation \(2 z ^ { 2 } - 2 z + 5 = 0\) satisfy \(| z - 2 | < \sqrt { 5 }\).
    ii. State, with a reason, which root of the equation \(2 z ^ { 2 } - 2 z + 5 = 0\) satisfies \(| z | < | z - 2 i |\).
    (d) On the same Argand diagram as part (b), indicate the positions of the roots of the equation \(2 z ^ { 2 } - 2 z + 5 = 0\).
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    [0pt]
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$$\begin{aligned}
& l _ { 1 } : \mathbf { r } = \left( \begin{array} { c } 
10 \\
3
\end{array} \right) + \lambda \left( \begin{array} { c } 
2 \\
- 2 \\
1
\end{array} \right) \\
& l _ { 2 } : \mathbf { r } = \left( \begin{array} { l } 
5 \\
2 \\
4
\end{array} \right) + \mu \left( \begin{array} { c } 
3 \\
1 \\
- 2
\end{array} \right)
\end{aligned}$$

$P$ is the point of intersection of $l _ { 1 }$ and $l _ { 2 }$.
\begin{enumerate}[label=(\alph*)]
\item Find the position vector of $P$.
\item Find, correct to 1 decimal place, the acute angle between $l _ { 1 }$ and $l _ { 2 }$.\\
$Q$ is a point on $l1$ which is 12 metres away from $P \cdot R$ is the point on $l2$ such that $QR$ is perpendicular to $l1$.
\item Determine the length $QR$.\\[0pt]
\\
5. (a) Express $\frac { 5 + 4 x - 3 x ^ { 2 } } { ( 1 - 2 x ) ( 2 + x ) ^ { 2 } }$ in three partial fractions.\\
(b)\\
Hence find the first three terms in the expansion of $\frac { 5 + 4 x - 3 x ^ { 2 } } { ( 1 - 2 x ) ( 2 + x ) ^ { 2 } }$ in ascending powers of $x$.\\
(c) State the set of values for which the expansion in part (b) is valid.\\[0pt]
\\
6.

The matrices $\mathbf { A }$ and $\mathbf { B }$ are given by $\mathbf { A } = \left( \begin{array} { l l } 1 & a \\ 3 & 0 \end{array} \right)$ and $\mathbf { B } = \left( \begin{array} { l l } 4 & 2 \\ 3 & 3 \end{array} \right)$.\\
(a) Find the value of a such that $\mathbf { A B } = \mathbf { B A }$.\\
(b) Prove by counter example that matrix multiplication for $2 \times 2$ matrices is not commutative.\\
(c) A triangle of area 4 square units is transformed by the matrix $\mathbf { B }$. Find the area of the image of the triangle following this transformation.
\item Find the equations of the invariant lines of the form $y = m x$ for the transformation represented by matrix $\mathbf { B }$.\\[0pt]
\\
7. (a) In this question you must show detailed reasoning.

Find the roots of the equation $2 z ^ { 2 } - 2 z + 5 = 0$.\\
(b) The loci $C _ { 1 }$ and $C _ { 2 }$ are given by $| z | = | z - 2 i |$ and $| z - 2 | = \sqrt { 5 }$ respectively.\\
i. Sketch on a single Argand diagram the loci $C _ { 1 }$ and $C _ { 2 }$, showing any intercepts with the imaginary axis.\\
ii. Indicate, by shading on your Argand diagram, the region $\{ z : | z | \leqslant | z - 2 \mathrm { i } | \} \cap \{ z : | z - 2 | \leqslant \sqrt { 5 } \}$.\\
(c) i. Show that both of the roots of the equation $2 z ^ { 2 } - 2 z + 5 = 0$ satisfy $| z - 2 | < \sqrt { 5 }$.\\
ii. State, with a reason, which root of the equation $2 z ^ { 2 } - 2 z + 5 = 0$ satisfies $| z | < | z - 2 i |$.\\
(d) On the same Argand diagram as part (b), indicate the positions of the roots of the equation $2 z ^ { 2 } - 2 z + 5 = 0$.\\[0pt]
\\[0pt]
\\[0pt]
\\[0pt]

\end{enumerate}

\hfill \mbox{\textit{SPS SPS FM 2024 Q10}}