Mathematics
Grade 12
15 min
Add and subtract scalar multiples of matrices
Add and subtract scalar multiples of matrices
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1
Introduction & Learning Objectives
Learning Objectives
Define a scalar and a matrix and identify their dimensions.
Perform scalar multiplication on a matrix of any dimension.
Determine if two matrices can be added or subtracted based on their dimensions.
Add or subtract two or more matrices of the same dimensions.
Evaluate complex expressions involving scalar multiplication, addition, and subtraction in the correct order.
Solve for an unknown matrix in a linear matrix equation.
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This tutorial covers the fundamental operations of matrix algebra: scalar multiplication, addition, and subtraction. Mastering these skills is essential for understandin...
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Key Concepts & Vocabulary
TermDefinitionExample
MatrixA rectangular array of numbers, symbols, or expressions arranged in rows and columns. The numbers in the array are called elements or entries.A = \begin{pmatrix} 5 & -1 & 7 \\ 2 & 0 & 4 \end{pmatrix} is a 2x3 matrix because it has 2 rows and 3 columns.
ScalarAn ordinary number, typically a real number, that is used to scale a matrix or vector.In the expression 3A, the number 3 is a scalar.
Dimensions of a MatrixThe size of a matrix, expressed as the number of rows by the number of columns (rows x columns).The matrix B = \begin{pmatrix} 1 \\ 2 \\ 3 \end{pmatrix} has dimensions 3x1.
Scalar MultiplicationThe operation of multiplying a matrix by a scalar. Every element inside the matrix is multiplied by the scalar.If k = 4 and A = \begin{pmatrix} 1...
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Core Formulas
Condition for Addition and Subtraction
Matrices A and B can be added or subtracted if and only if they have the exact same dimensions (i.e., same number of rows and same number of columns).
Before attempting to add or subtract, always check the dimensions. If matrix A is m x n, matrix B must also be m x n. The resulting matrix will also have dimensions m x n.
Scalar Multiplication Formula
If k is a scalar and A = [a_{ij}], then kA = [k \cdot a_{ij}].
To perform scalar multiplication, you multiply every single element in the matrix A by the scalar k. The dimensions of the matrix do not change.
Matrix Addition and Subtraction Formula
If A = [a_{ij}] and B = [b_{ij}], then A \pm B = [a_{ij} \pm b_{ij}].
To add or subtract matrices with the same dimensions, you add or su...
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Challenging
Solve the following system of matrix equations for matrix X: X + Y = \begin{pmatrix} 8 & 1 \ 7 & 6 \end{pmatrix} and X - Y = \begin{pmatrix} 2 & 3 \ -1 & 0 \end{pmatrix}
A.\begin{pmatrix} 5 & 2 \ 3 & 3 \end{pmatrix}
B.\begin{pmatrix} 3 & -1 \ 4 & 3 \end{pmatrix}
C.\begin{pmatrix} 10 & 4 \ 6 & 6 \end{pmatrix}
D.\begin{pmatrix} 6 & -2 \ 8 & 6 \end{pmatrix}
Challenging
Given the equation 2\begin{pmatrix} x & 3 \ -1 & y \end{pmatrix} - \begin{pmatrix} 4 & z \ 5 & -2 \end{pmatrix} = \begin{pmatrix} 10 & 0 \ -7 & 8 \end{pmatrix}, find the values of x, y, and z.
A.x = 5, y = 5, z = 3
B.x = 7, y = 4, z = -6
C.x = 7, y = 3, z = 6
D.x = 3, y = 3, z = 6
Challenging
Let A be any 2x2 matrix and let 0 be the 2x2 zero matrix (all elements are zero). Which expression is equivalent to 3A - (A + 0)?
A.3A
B.2A
C.The 2x2 zero matrix
D.A
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