If w, x, y, and z are real numbers satisfying:
w + x + y = -2
w + x + z = 4
w + y + z = 9
x + y + z = 2
what is wx + yz?
Nice problem! Adding all the equations gives us
3(w + x + y + z) = 13
w + x + y + z = 13/3
The first equation becomes(Can you see how I did this?):
(w + x + y + z) - z = -2
Doing this step and solving the other variables, can you continue from here?
Now solve this https://web2.0calc.com/questions/need-help-with-this_18
