A matrix is a rectangular array of numbers. An m times n matrix has m rows and n columns. [formula] Addition/Subtraction: Add corresponding entries. Matri…
A matrix is a rectangular array of numbers. An m times n matrix has m rows and n columns. [formula] Addition/Subtraction: Add corresponding entries. Matrices must be the same size. Scalar multiplication: Multiply every entry by the scalar. Matrix multiplication: A_{m times n} cdot B_{n times p} = C_{m times p}. The number of columns of A must equal the number of rows of B. Each entry: row of …
Example: Multiply begin{pmatrix} 1 & 2 3 & 4 end{pmatrix} begin{pmatrix} 5 6 end{pmatrix}
Matrix multiplication questions on the ACT are usually 2×2 times 2×1 or 2×2 times 2×2. The key: row times column, dot product style. Practice the pattern 3 times and it becomes automatic.
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