Question

Given the following matrices, if possible, determine 4A - 2B. if not, state “not possible”

Answer 1

To subtract two matrices they have to be of the same size. Now, a matrix C by a scalar is also a matrix of the same size of matrix C with entries equal to the product of the scalar by the value of the entry in matrix C.

Therefore:

`\begin{gathered} 4A=4\lbrack1\text{ 4 -2}\rbrack=\lbrack4\text{ 16 -8}\rbrack, \\ -2B=-2\lbrack-1\text{ 6 0}\rbrack=\lbrack2\text{ -12 0}\rbrack. \end{gathered}`

Adding the above matrices we get:

`4A-2B=\lbrack4\text{ 16 -8}\rbrack+\lbrack2\text{ -12 0}\rbrack=\lbrack6\text{ 4 -8}\rbrack.`

Answer:

`4A-2B=\lbrack6\text{ 4 -8}\rbrack`