10.12 Homework: calculators

Solve on a calculator: $\left[\begin{array}{ccc}1& 2& 3\\ 4& 5& 6\end{array}\right]$ + $\left[\begin{array}{ccc}7& 8& 9\\ \text{10}& \text{11}& \text{12}\end{array}\right]$

Solve on a calculator: $\left[\begin{array}{ccc}1& 2& 3\\ 4& 5& 6\end{array}\right]$ – $\left[\begin{array}{ccc}7& 8& 9\\ \text{10}& \text{11}& \text{12}\end{array}\right]$

Solve on a calculator: $\left[\begin{array}{ccc}1& 2& 3\\ 4& 5& 6\end{array}\right]$ $\left[\begin{array}{ccc}7& 8& 9\\ \text{10}& \text{11}& \text{12}\end{array}\right]$

Find the inverse of the matrix $\left[\begin{array}{ccc}1& 2& 8\\ 4& 5& 6\\ 7& 8& 9\end{array}\right]$ .

Multiply the matrix $\left[\begin{array}{ccc}1& 2& 8\\ 4& 5& 6\\ 7& 8& 9\end{array}\right]$ by its own inverse. What do you get? Is it what you expected?

Matrix $A$ is $\left[\begin{array}{ccc}6& 1& 2\\ 0& 9& 5\end{array}\right]$ . Matrix $B$ is $\left[\begin{array}{ccc}\text{10}& -2& 3\\ 4& 7& 0\end{array}\right]$ . Matrix $C$ is $\left[\begin{array}{cc}-6& \text{12}\\ 9& 7\\ 3& 2\end{array}\right]$ . Use your calculator to find…

• A

  $\mathrm{AC}$

• B

  $\mathrm{CA}$

• C

  $(A+B)C$

• D

  $2A+\frac{1}{2}B$