Answer:
The product of given
is ![\left[\begin{array}{ccc}-32 \\4\\20\\-36\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7D-32%20%5C%5C4%5C%5C20%5C%5C-36%5Cend%7Barray%7D%5Cright%5D)
Step-by-step explanation:
Consider the given product of a constant and a matrix.
![-4 \cdot \left[\begin{array}{ccc}8\\-1\\-5\\9\end{array}\right]](https://tex.z-dn.net/?f=-4%20%5Ccdot%20%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7D8%5C%5C-1%5C%5C-5%5C%5C9%5Cend%7Barray%7D%5Cright%5D)
To do product we multiply scalar -4 with each element of the matrix given,
![-4 \cdot \left[\begin{array}{ccc}8\\-1\\-5\\9\end{array}\right]= \left[\begin{array}{ccc}-4 \times 8 \\-4 \times -1\\-4 \times -5\\-4 \times 9\end{array}\right]](https://tex.z-dn.net/?f=-4%20%5Ccdot%20%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7D8%5C%5C-1%5C%5C-5%5C%5C9%5Cend%7Barray%7D%5Cright%5D%3D%20%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7D-4%20%5Ctimes%208%20%5C%5C-4%20%5Ctimes%20-1%5C%5C-4%20%5Ctimes%20-5%5C%5C-4%20%5Ctimes%209%5Cend%7Barray%7D%5Cright%5D)
On solving further , we get,
![\left[\begin{array}{ccc}-4 \times 8 \\-4 \times -1\\-4 \times -5\\-4 \times 9\end{array}\right]=\left[\begin{array}{ccc}-32 \\4\\20\\-36\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7D-4%20%5Ctimes%208%20%5C%5C-4%20%5Ctimes%20-1%5C%5C-4%20%5Ctimes%20-5%5C%5C-4%20%5Ctimes%209%5Cend%7Barray%7D%5Cright%5D%3D%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7D-32%20%5C%5C4%5C%5C20%5C%5C-36%5Cend%7Barray%7D%5Cright%5D)
Thus, the product of given
is ![\left[\begin{array}{ccc}-32 \\4\\20\\-36\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7D-32%20%5C%5C4%5C%5C20%5C%5C-36%5Cend%7Barray%7D%5Cright%5D)
Jake spent a total of 70 cents.
b = black-and-white = 8 cents
c = color = 15 cents
70 = 8b + 15c
he made a total of 7 copies
b + c = 7
system of equation:
70 = 8b + 15c
b + c = 7
--------------------------
b + c = 7
b + c (-c) = 7 (-c)
b = 7 - c
plug in 7 - c for b
70 = 8(7 - c) + 15c
Distribute the 8 to both 7 and - c (distributive property)
70 = 56 - 8c + 15c
Simplify like terms
70 = 56 - 8c + 15c
70 = 56 + 7c
Isolate the c, do the opposite of PEMDAS: Subtract 56 from both sides
70 (-56) = 56 (-56) + 7c
14 = 7c
divide 7 from both sides to isolate the c
14 = 7c
14/7 = 7c/7
c = 14/7
c = 2
c = 2
---------------
Now that you know what c equals (c = 2), plug in 2 for c in one of the equations.
b + c = 7
c = 2
<em>b + (2) = 7
</em><em />Find b by isolating it. subtract 2 from both sides
b + 2 = 7
b + 2 (-2) = 7 (-2)
b = 7 - 2
b = 5
Jake made 5 black-and-white copies, and 2 color copies
hope this helps