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78
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Can someone please help me on this problem

 Nov 26, 2021
 #1
avatar
0

We can write the system as

\(\begin{pmatrix} 1 & 1 & 1 & 0 \\ 1 & 1 & 0 & 1 \\ 1 & 0 & 1 & 1 \\ 0 & 1 & 1 & 1 \end{pmatrix} \begin{pmatrix} w \\ x \\ y \\ z \end{pmatrix} = \begin{pmatrix} -2 \\ 4 \\ 19 \\ 12 \end{pmatrix}\)

The solution is then (w,x,y,z) = (-3,-7,8,14), so wx + yz = (-3)(-7) + (8)(14) = 133.

 Nov 27, 2021
 #3
avatar+1679 
+3

Plug the values of x, y, and z into this equation:  x + y + z = 12

civonamzuk  Nov 27, 2021
 #2
avatar+1679 
+3

w + x + y = - 2

________________

w + y + z = 19

x + y + z =  12

--------- w = x + 7  (1)

 

w + x + z = 4

w + y + z = 19

--------- y = x + 15   (2)

_________________

w + x + y = - 2

x = - 2 - w - y

x = - 2 - (x + 7) - (x + 15) 

x = - 8

w = - 1

y = 7

z = 13

---------------------

wx + yz = (- 1)(- 8) + 7(13) = 99

 Nov 27, 2021

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