Solving Linear Equations Programmatically Without a Math Library

Every developer eventually needs to solve a system of linear equations. Maybe you are building a pricing model, fitting a trendline, balancing a physics simulation, or solving a constraint satisfaction problem. Reaching for a math library is the pragmatic choice, but understanding the underlying algorithm makes you a better debugger when things go wrong. What a linear equation system looks like A system of two linear equations in two variables: 2x + 3y = 8 4x - y = 2 In matrix form, this is Ax = b: | 2 3 | | x | | 8 | | 4 -1 | | y | = | 2 | The goal is to find values of x and y that satisfy both equations simultaneously. Solving a 2x2 system with Cramer's Rule For a 2x2 system, Cramer's Rule is the fastest approach: function solve2x2(a1, b1, c1, a2, b2, c2) { // a1*x + b1*y = c1 // a2*x + b2*y = c2 const det = a1 * b2 - a2 * b1; if (Math.abs(det) < 1e-10) { return null; // No unique solution } const x = (c1 * b2 - c2 * b1) / det; const y = (a1 * c2 - a2 * c1) / det; return { x, y };