Question

If a= (-3 -9 -3 -4 -3 9 7 9 -10) and b= (9 1 6 3 -10 5 -1 9 -9) find -7A -4B?​

Answer 1

To find -7A - 4B, we multiply each element of vector A and vector B by their respective constants, then subtract the resulting vectors.

Step-by-step explanation:

To find -7A - 4B, we first need to multiply each element of vector A and vector B by their respective constants. Then, we subtract the resulting vectors.

Given A = (-3, -9, -3, -4, -3, 9, 7, 9, -10) and B = (9, 1, 6, 3, -10, 5, -1, 9, -9),

-7A = (-7)(-3, -9, -3, -4, -3, 9, 7, 9, -10) = (21, 63, 21, 28, 21, -63, -49, -63, 70)

-4B = (-4)(9, 1, 6, 3, -10, 5, -1, 9, -9) = (-36, -4, -24, -12, 40, -20, 4, -36, 36)

-7A - 4B = (21, 63, 21, 28, 21, -63, -49, -63, 70) - (-36, -4, -24, -12, 40, -20, 4, -36, 36) = (57, 67, 45, 40, -19, -43, -53, -27, 34)

Answer 2

Answer: Choice A

`\begin{pmatrix}-15 & 59 & -3\\16 & 61 & -83\\-45 & -99 & 106\end{pmatrix}`

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Step-by-step explanation:

In matrix A, the upper left corner is -3

Multiply this with -7 to get -7*(-3) = 21

So we'll have 21 in the upper left corner of matrix -7A. The other entries will be handled in a similar fashion.

Meanwhile, the upper left corner of matrix B is 9. Multiply this with -4 to get 9(-4) = -36 which is the upper left corner entry of matrix -4B

Combine those products: 21 + (-36) = -15

The number -15 is the upper left corner entry in matrix -7A-4B

This points us to choice A as the final answer.