Finite Math Examples

$6 a - 4 b = [\begin{array}{c} - 3 & 8 \\ 4 & 4 \end{array}] - 4 [\begin{array}{c} 1 & 0 \\ 0 & 1 \end{array}]$

Step 1

Multiplying the identity matrix by any matrix $A$ is the matrix $A$ itself.

$6 a - 4 b = [\begin{array}{c} - 3 & 8 \\ 4 & 4 \end{array}] - 4$

Step 2

Simplify the right side.

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Step 2.1

Adding $- 4$ to a $2 \times 2$ square matrix is the same as adding $- 4$ times the $2 \times 2$ identity matrix.

$6 a - 4 b = [\begin{array}{c} - 3 & 8 \\ 4 & 4 \end{array}] - 4 [\begin{array}{c} 1 & 0 \\ 0 & 1 \end{array}]$

Step 2.2

Multiply $- 4$ by each element of the matrix.

$6 a - 4 b = [\begin{array}{c} - 3 & 8 \\ 4 & 4 \end{array}] + [\begin{array}{c} - 4 \cdot 1 & - 4 \cdot 0 \\ - 4 \cdot 0 & - 4 \cdot 1 \end{array}]$

Step 2.3

Simplify each element in the matrix.

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Step 2.3.1

Multiply $- 4$ by $1$ .

$6 a - 4 b = [\begin{array}{c} - 3 & 8 \\ 4 & 4 \end{array}] + [\begin{array}{c} - 4 & - 4 \cdot 0 \\ - 4 \cdot 0 & - 4 \cdot 1 \end{array}]$

Step 2.3.2

Multiply $- 4$ by $0$ .

$6 a - 4 b = [\begin{array}{c} - 3 & 8 \\ 4 & 4 \end{array}] + [\begin{array}{c} - 4 & 0 \\ - 4 \cdot 0 & - 4 \cdot 1 \end{array}]$

Step 2.3.3

Multiply $- 4$ by $0$ .

$6 a - 4 b = [\begin{array}{c} - 3 & 8 \\ 4 & 4 \end{array}] + [\begin{array}{c} - 4 & 0 \\ 0 & - 4 \cdot 1 \end{array}]$

Step 2.3.4

Multiply $- 4$ by $1$ .

$6 a - 4 b = [\begin{array}{c} - 3 & 8 \\ 4 & 4 \end{array}] + [\begin{array}{c} - 4 & 0 \\ 0 & - 4 \end{array}]$

Step 2.4

Add the corresponding elements.

$6 a - 4 b = [\begin{array}{c} - 3 - 4 & 8 + 0 \\ 4 + 0 & 4 - 4 \end{array}]$

Step 2.5

Simplify each element.

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Step 2.5.1

Subtract $4$ from $- 3$ .

$6 a - 4 b = [\begin{array}{c} - 7 & 8 + 0 \\ 4 + 0 & 4 - 4 \end{array}]$

Step 2.5.2

Add $8$ and $0$ .

$6 a - 4 b = [\begin{array}{c} - 7 & 8 \\ 4 + 0 & 4 - 4 \end{array}]$

Step 2.5.3

Add $4$ and $0$ .

$6 a - 4 b = [\begin{array}{c} - 7 & 8 \\ 4 & 4 - 4 \end{array}]$

Step 2.5.4

Subtract $4$ from $4$ .

$6 a - 4 b = [\begin{array}{c} - 7 & 8 \\ 4 & 0 \end{array}]$