Practice Solving Systems of Equations with Matrices in Math

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Quick Recap

Systems of linear equations can be represented as the matrix equation Ax=bAx = b and solved using augmented matrices with row reduction (Gaussian elimination), matrix inverses (x=Aβˆ’1bx = A^{-1}b), or Cramer's rule (using determinants).

Instead of juggling multiple equations with substitution or elimination, pack everything into a matrix and use systematic row operations. It is like organizing a messy deskβ€”once the equations are neatly arranged in a matrix, a mechanical process (row reduction) reveals the answer. Each row operation is an allowed algebraic move (swap equations, scale an equation, add equations) performed on the matrix.

Showing a random 20 of 50 problems.

Example 1

easy
Which row operation swaps two rows?

Example 2

easy
Write {x=3y=5\begin{cases} x = 3 \\ y = 5 \end{cases} as a solution vector.

Example 3

challenge
Solve the system {2x+y=4xβˆ’y=βˆ’1\begin{cases} 2x + y = 4 \\ x - y = -1 \end{cases} three ways agree: give the solution.

Example 4

medium
Use x=Aβˆ’1bx = A^{-1}b to solve Ax=bA x = b where A=(2153)A = \begin{pmatrix} 2 & 1 \\ 5 & 3 \end{pmatrix} and b=(411)b = \begin{pmatrix} 4 \\ 11 \end{pmatrix}.

Example 5

easy
Solve by inspection: (100010001)(xyz)=(4βˆ’27)\begin{pmatrix} 1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1 \end{pmatrix}\begin{pmatrix} x \\ y \\ z \end{pmatrix} = \begin{pmatrix} 4 \\ -2 \\ 7 \end{pmatrix}.

Example 6

easy
If the coefficient matrix has determinant 0, what does it tell you about the solution?

Example 7

easy
In Cramer's rule for Ax=bAx = b, what is each variable a ratio of?

Example 8

challenge
Use Cramer's rule to find only yy in {3x+2y=7x+4y=9\begin{cases} 3x + 2y = 7 \\ x + 4y = 9 \end{cases}.

Example 9

hard
Find all kk for which {x+2y=k2x+4y=6\begin{cases} x + 2y = k \\ 2x + 4y = 6 \end{cases} has infinitely many solutions.

Example 10

easy
What is the augmented matrix of {2xβˆ’y=3x+4y=7\begin{cases} 2x - y = 3 \\ x + 4y = 7 \end{cases}?

Example 11

medium
Use Cramer's rule to solve {2x+y=5x+3y=10\begin{cases} 2x + y = 5 \\ x + 3y = 10 \end{cases}.

Example 12

medium
Find det⁑(A)\det(A) for A=(3214)A = \begin{pmatrix} 3 & 2 \\ 1 & 4 \end{pmatrix} to confirm a unique solution exists.

Example 13

easy
Write the augmented matrix for {x+2y=43x+y=5\begin{cases} x + 2y = 4 \\ 3x + y = 5 \end{cases}.

Example 14

medium
Solve {x+y=5xβˆ’y=1\begin{cases} x + y = 5 \\ x - y = 1 \end{cases} by elimination.

Example 15

easy
Write the coefficient matrix for {2x+3y=5xβˆ’y=1\begin{cases} 2x + 3y = 5 \\ x - y = 1 \end{cases}.

Example 16

medium
Solve {3xβˆ’y=52x+y=5\begin{cases} 3x - y = 5 \\ 2x + y = 5 \end{cases} by elimination.

Example 17

medium
What does an augmented matrix row (004)\left(\begin{array}{cc|c} 0 & 0 & 4 \end{array}\right) indicate?

Example 18

easy
Find Aβˆ’1A^{-1} for A=(2003)A = \begin{pmatrix} 2 & 0 \\ 0 & 3 \end{pmatrix}.

Example 19

challenge
Find det⁑ ⁣(1aa21bb21cc2)\det\!\begin{pmatrix} 1 & a & a^2 \\ 1 & b & b^2 \\ 1 & c & c^2 \end{pmatrix} in factored form.

Example 20

easy
Identify the coefficient matrix of {x+y+z=12yβˆ’z=0x+z=5\begin{cases} x + y + z = 1 \\ 2y - z = 0 \\ x + z = 5 \end{cases}.