Mathematics
Grade 12
15 min
Add and subtract matrices
Add and subtract matrices
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1
Introduction & Learning Objectives
Learning Objectives
Identify the dimensions of a matrix and determine if two matrices can be added or subtracted.
Perform element-wise addition on two or more matrices of the same dimensions.
Perform element-wise subtraction on two matrices of the same dimensions.
Apply the commutative and associative properties of matrix addition to simplify expressions.
Solve for an unknown matrix in simple algebraic equations involving addition and subtraction.
Combine scalar multiplication with matrix addition and subtraction to evaluate complex matrix expressions.
How do businesses track and combine sales data from multiple stores to get a company-wide total? They use matrices! 📊
This tutorial will guide you through the fundamental operations of matrix addition and subtraction. You wi...
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Key Concepts & Vocabulary
TermDefinitionExample
MatrixA rectangular array of numbers, symbols, or expressions, arranged in rows and columns. A matrix is typically enclosed in square brackets.A = \begin{bmatrix} 2 & -1 & 0 \\ 3 & 5 & 9 \end{bmatrix}
Dimensions of a MatrixThe size of a matrix, described by its number of rows and columns, written as 'rows × columns'.The matrix \begin{bmatrix} 2 & -1 & 0 \\ 3 & 5 & 9 \end{bmatrix} has 2 rows and 3 columns, so its dimensions are 2 × 3.
Elements (or Entries)The individual values within a matrix. An element's position is denoted by its row and column index, a_ij, where 'i' is the row and 'j' is the column.In the matrix A = \begin{bmatrix} 2 & -1 \\ 3 & 5 \end{bmatrix}, the element a_21 is 3.
Corre...
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Core Formulas
Condition for Matrix Addition and Subtraction
Matrices A and B can be added or subtracted if and only if they have the exact same dimensions (m × n).
This is the most critical rule. If the dimensions do not match, the operation is undefined. You cannot add a 2 × 3 matrix to a 3 × 2 matrix.
Matrix Addition
If A = [a_ij] and B = [b_ij] are both m × n matrices, their sum is C = A + B, where c_ij = a_ij + b_ij.
To add two matrices, you add their corresponding elements. The resulting matrix will have the same dimensions as the original matrices.
Matrix Subtraction
If A = [a_ij] and B = [b_ij] are both m × n matrices, their difference is D = A - B, where d_ij = a_ij - b_ij.
To subtract matrix B from matrix A, you subtract each element of B from the corresponding element of...
5 more steps in this tutorial
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Challenging
Let matrices X and Y satisfy the following two equations: X + Y = \begin{bmatrix} 5 & 2 \\ 1 & 6 \end{bmatrix} and X - Y = \begin{bmatrix} 1 & 0 \\ 3 & -2 \end{bmatrix}. Find the matrix X.
A.\begin{bmatrix} 2 & 1 \\ -1 & 4 \end{bmatrix}
B.\begin{bmatrix} 4 & 2 \\ 4 & 4 \end{bmatrix}
C.\begin{bmatrix} 3 & 1 \\ 2 & 2 \end{bmatrix}
D.\begin{bmatrix} 6 & 2 \\ 4 & 4 \end{bmatrix}
Challenging
Let A be a matrix of dimensions m × (2k-1) and B be a matrix of dimensions (m+1) × n. For the operation A - B to be defined, what must be the relationship between m, n, and k?
A.m = m+1 and 2k-1 = n
B.m = n and 2k-1 = m+1
C.The operation is never defined.
D.m = 2k-1 and n = m+1
Challenging
Given A = \begin{bmatrix} 1 & 0 \\ 4 & -2 \end{bmatrix} and B = \begin{bmatrix} 0 & 2 \\ -1 & 5 \end{bmatrix}, find the matrix X that solves the equation 3A - 2X = 5B.
A.\begin{bmatrix} 1.5 & -5 \\ 8.5 & -15.5 \end{bmatrix}
B.\begin{bmatrix} 3 & -10 \\ 17 & -31 \end{bmatrix}
C.\begin{bmatrix} 3 & 10 \\ -17 & 31 \end{bmatrix}
D.\begin{bmatrix} 1.5 & 5 \\ -8.5 & 15.5 \end{bmatrix}
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