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Cramer's Rule

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May 1, 2024 4 minute read

Cramer's Rule is a method for solving systems of linear equations with the same number of equations as variables. It is named after Gabriel Cramer, a Swiss mathematician who first published the rule in 1750.

Cramer's Rule Formula

Cramer's Rule states that the solution to a system of linear equations is given by,
Solution of x = (Determinant of numerator)/Determinant of whole matrix

where the determinant of the numerator is the determinant of the matrix formed by replacing the column of coefficients of the variable being solved for with the column of constants, and the determinant of the whole matrix is the determinant of the matrix of coefficients.

Example

For example, consider the following system of equations:
x + 2y = 5
3x + 4y = 8

Using Cramer's Rule, we can solve for x as follows:
Determinant of numerator =
|5 2|
|8 4| = 20 - 16 = 4
Determinant of whole matrix =
|1 2|
|3 4| = 4 - 6 = -2
So, x = 4/-2 = -2.

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Reading list

We've selected five books that we think will supplement your learning. Use these to develop background knowledge, enrich your coursework, and gain a deeper understanding of the topics covered in Cramer's Rule.
This classic work by Gabriel Cramer is the original source of Cramer's Rule. It provides a detailed exposition of the rule and its applications in geometry and physics.
Develops a computational approach to Cramer's Rule that makes it more efficient to use in practice. It is suitable for researchers and practitioners who need to solve large systems of linear equations.
This beginner-friendly book provides a step-by-step guide to using Cramer's Rule. It is ideal for students who are new to the subject or who need a refresher.
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