Algebraic and Analytic Geometry
《Algebraic and Analytic Geometry》 · 第 169 页 · Section 3.3「Systems of Linear Equations—Theoretical Aspects」，定义段
The equations $a_{i1}x_1+a_{i2}x_2+\cdots+a_{in}x_n=b_i$ for $1\le i\le m$ are called a system of $m$ linear equations in the $n$ unknowns $x_1,x_2,\ldots,x_n$ over the field $F$.