Physics Lournal

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a11x1+a12x2+…+a1nxn=b1 a21x1+a22x2+…+a2nxn=b2 ⋮ am1x1+am2x2+…+amnxn=bm\begin{array}{lcl} a_{11}x_1 + a_{12}x_2 + \ldots + a_{1n}x_n = b_1 \ a_{21}x_1 + a_{22}x_2 + \ldots + a_{2n}x_{n} = b_2 \ \vdots \ a_{m1}x_1 + a_{m2}x_2 + \ldots + a_{mn}x_n = b_m \end{array}

The double subscript on coefficients aija{ij} gives their location in the system, with the i_{i} indication the equation in which the coefficient appears, and the j_{j} indicating the unknown it multiplies.

A solution for a system is the the sequence of numbers that, when substituted for the unknowns (xix_i), makes each equation a true statement.

Alternatively, they can be seen as matrix coordinates, with the first subscript indicating the row the coefficient is located in, and the second indicating the column the coefficient is located in.