### Home > A2C > Chapter 7 > Lesson 7.3.3 > Problem7-187

7-187.

Perform each of the following matrix operations without using a calculator. If the operation is impossible, explain why.

1. $\left[ \begin{array} { l l l } { 4 } & { 9 } & { 2 } \\ { 6 } & { 0 } & { 5 } \end{array} \right] \left[ \begin{array} { l } { a } \\ { b } \\ { c } \end{array} \right]$

What have you learned about matrix operations so far?

1. $2 \left[ \begin{array} { c c c } { 4 } & { 9 } & { 2 } \\ { 6 } & { 0 } & { - 5 } \end{array} \right] + \left[ \begin{array} { c c c } { 1 } & { 0 } & { - 3 } \\ { 0 } & { 4 } & { 1 } \end{array} \right]$

Multiply through by the 2 before you add.

1. $\\ \left[ \begin{array} { l l } { a } & { b } \\ { c } & { d } \end{array} \right] \left[ \begin{array} { l l } { e } & { f } \end{array} \right]$

What must be true about the dimensions of two matrices in order to multiply them?

1. $\left[ \begin{array} { l l } { a } & { b } \\ { c } & { d } \end{array} \right] + \left[ \begin{array} { l l } { e } & { f } \end{array} \right]$

What must be true about the dimensions of two matrices in order to add them?