CAIE FP1 2017 June — Question 11 OR

Exam BoardCAIE
ModuleFP1 (Further Pure Mathematics 1)
Year2017
SessionJune
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
Topic3x3 Matrices
TypeRank and null space basis
DifficultyChallenging +1.8 This is a substantial Further Maths question requiring row reduction to find rank, verification of null space basis vectors, solving a non-homogeneous linear system using particular + homogeneous solutions, and determining consistency conditions. While methodical rather than requiring deep insight, it demands fluency with multiple linear algebra techniques and careful algebraic manipulation across three connected parts, placing it well above average difficulty.
Spec4.03a Matrix language: terminology and notation4.03r Solve simultaneous equations: using inverse matrix

The matrix \(\mathbf { A }\), given by $$\mathbf { A } = \left( \begin{array} { r r r r } 1 & - 1 & 0 & 2 \\ 3 & - 1 & 4 & 0 \\ 5 & - 8 & - 6 & 19 \\ - 2 & 3 & 2 & - 7 \end{array} \right) ,$$ represents a transformation from \(\mathbb { R } ^ { 4 }\) to \(\mathbb { R } ^ { 4 }\).
  1. Find the rank of \(\mathbf { A }\) and show that \(\left\{ \left( \begin{array} { r } 2 \\ 2 \\ - 1 \\ 0 \end{array} \right) , \left( \begin{array} { l } 1 \\ 3 \\ 0 \\ 1 \end{array} \right) \right\}\) is a basis for the null space of the transformation. \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\)
  2. Show that if $$\mathbf { A x } = p \left( \begin{array} { r } 1 \\ 3 \\ 5 \\ - 2 \end{array} \right) + q \left( \begin{array} { r } - 1 \\ - 1 \\ - 8 \\ 3 \end{array} \right) ,$$ where \(p\) and \(q\) are given real numbers, then $$\mathbf { x } = \left( \begin{array} { c } p + 2 \lambda + \mu \\ q + 2 \lambda + 3 \mu \\ - \lambda \\ \mu \end{array} \right) ,$$ where \(\lambda\) and \(\mu\) are real numbers. \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\)
  3. Find the values of \(p\) and \(q\) such that $$p \left( \begin{array} { r } 1 \\ 3 \\ 5 \\ - 2 \end{array} \right) + q \left( \begin{array} { r } - 1 \\ - 1 \\ - 8 \\ 3 \end{array} \right) = \left( \begin{array} { r } 3 \\ 7 \\ 18 \\ - 7 \end{array} \right)$$ \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\)
  4. Find the solution of the equation \(\mathbf { A x } = \left( \begin{array} { r } 3 \\ 7 \\ 18 \\ - 7 \end{array} \right)\) of the form \(\mathbf { x } = \left( \begin{array} { l } 4 \\ 9 \\ \alpha \\ \beta \end{array} \right)\), where \(\alpha\) and \(\beta\) are positive integers to be found. \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\) \(\_\_\_\_\)

The matrix $\mathbf { A }$, given by

$$\mathbf { A } = \left( \begin{array} { r r r r } 
1 & - 1 & 0 & 2 \\
3 & - 1 & 4 & 0 \\
5 & - 8 & - 6 & 19 \\
- 2 & 3 & 2 & - 7
\end{array} \right) ,$$

represents a transformation from $\mathbb { R } ^ { 4 }$ to $\mathbb { R } ^ { 4 }$.\\
(i) Find the rank of $\mathbf { A }$ and show that $\left\{ \left( \begin{array} { r } 2 \\ 2 \\ - 1 \\ 0 \end{array} \right) , \left( \begin{array} { l } 1 \\ 3 \\ 0 \\ 1 \end{array} \right) \right\}$ is a basis for the null space of the transformation.\\
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(ii) Show that if

$$\mathbf { A x } = p \left( \begin{array} { r } 
1 \\
3 \\
5 \\
- 2
\end{array} \right) + q \left( \begin{array} { r } 
- 1 \\
- 1 \\
- 8 \\
3
\end{array} \right) ,$$

where $p$ and $q$ are given real numbers, then

$$\mathbf { x } = \left( \begin{array} { c } 
p + 2 \lambda + \mu \\
q + 2 \lambda + 3 \mu \\
- \lambda \\
\mu
\end{array} \right) ,$$

where $\lambda$ and $\mu$ are real numbers.\\
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(iii) Find the values of $p$ and $q$ such that

$$p \left( \begin{array} { r } 
1 \\
3 \\
5 \\
- 2
\end{array} \right) + q \left( \begin{array} { r } 
- 1 \\
- 1 \\
- 8 \\
3
\end{array} \right) = \left( \begin{array} { r } 
3 \\
7 \\
18 \\
- 7
\end{array} \right)$$

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(iv) Find the solution of the equation $\mathbf { A x } = \left( \begin{array} { r } 3 \\ 7 \\ 18 \\ - 7 \end{array} \right)$ of the form $\mathbf { x } = \left( \begin{array} { l } 4 \\ 9 \\ \alpha \\ \beta \end{array} \right)$, where $\alpha$ and $\beta$ are positive integers to be found.\\
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\hfill \mbox{\textit{CAIE FP1 2017 Q11 OR}}