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If w, x, y, and z are real numbers satisfying:

what is wx + yz?

 

thanks in advance!!

 Sep 4, 2022
 #1
avatar+39 
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https://web2.0calc.com/questions/help_50204

 

The answer is \(99\) but read through the whole thing to see why

 Sep 4, 2022
 #2
avatar+2455 
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Here's a way without matrixes: 

 

Adding all 4 equations gives us \(3(w+x+y+z) = 33\), meaning \(w+ x + y + z = 11\).

 

Using this, we know \(w = -1\)\(x = -8\)\(y = 7\), and \(z = 13\)

 

So, we have \((-1 \times -8) + (7 \times 13) = \color{brown}\boxed{99}\)

 Sep 6, 2022

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