Question

If A=
`\left[\begin{array}{ccc}-10&10&8\\-2&-1&5\\-4&8&-6\end{array}\right]` and B=
`\left[\begin{array}{ccc}5&6&-4\\10&-6&-10\\-9&1&10\end{array}\right]` , find -7A and -6B.

Answer 1

Option c

Explanation:

We have two matrices, matrix A and matrix B.

Before doing the addition of matrices, we must multiply the matrix A by the scalar -7 and then multiply the matrix B by the scalar -6.

The multiplication of a matrix A by a scalar c, is done by multiplying all the elements of matrix A by the value c.

So

`-7A = \left[\begin{array}{ccc}70&-70&-56\\14&7&-35\\28&-56&42\end{array}\right]\\\\\\-6B =\left[\begin{array}{ccc}-30&-36&24\\-60&36&60\\54&-6&-60\end{array}\right]`

Now we add both matrices.

The sum of the matrices is done by adding each term
`a_(mn)` with each term
`b_(mn)`

For example: (70 - 40) , (-70 + (-36)), ...,

Then:

`-7A + (-6B) = \left[\begin{array}{ccc}40&-106&-32\\-46&43&25\\82&-62&-18\end{array}\right]`