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Using Matrices to Solve a System of Equations or Simultaneous Equations




 
In these lessons, we will how to solve Systems of Equations or Simultaneous Equations using Matrices.

Related Topics:
Solving Systems of Equations or Simultaneous Equations using algebra, More Algebra Lessons

Matrices and Inverse Matrices

Simultaneous equations or system of equations of the form ax + by = h and cx + dy = k can be solved using algebra. Simultaneous equations can also be solved using matrices.

First, we would look at how the inverse of a matrix can be used to solve a matrix equation.

Given the matrix equation AY = B, find the matrix Y.

If we multiply each side of the equation by A-1, we get

A-1A Y = A-1B

I Y = A -1B    ( AA -1= I, where I is the identity matrix)

Y = A -1B       ( IY = Y, any matrix multiply with the identity matrix will be unchanged)


Matrices & Systems of Equations

Example:

Using matrices, calculate the values of x and y for the following simultaneous equations:

2x – 2y – 3 = 0

8 y = 7x + 2

Solution:

Step 1: Write the equations in the form ax + by = c

2x – 2y – 3 = 0 ⇒ 2x – 2y = 3

8y = 7x + 2 ⇒ 7x – 8y = –2

Step 2: Write the equations in matrix form.

 

Step 3: Find the inverse of the 2 × 2 matrix.

Determinant = (2 × –8) – (–2 × 7) = – 2

Step 4: Multiply both sides of the matrix equations with the inverse

So, x = 14 and y = 12.5



Videos

The following video shows how matrices can be used to solve a system of equations.
Using the inverse of a matrix to solve a system of equations.
Using a Matrix Equation to Solve a System of Equations
This video shows how to solve a system of equations by using a matrix equation.
A 2 x 2 example and a 3 x 3 example are given.
The graphing calculator is integrated into the lesson.


 
Solving Simultaneous Equations Using Matrices.
Step by step solution.
Simultaneous Equations - Matrix Method.


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You can use the free Mathway widget below to practice Algebra or other math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.


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