Respuesta :

x=y has infinite solutions.
xy=0 is another example.
x - 2y = 2 and 2x - 4y = 4

solve: 
multiply (1st) equation by 2
2x - 4y = 4

Now you have
 2x - 4y = 4
 2x - 4y = 4
-------------------subtract
0 = 0

This is infinitely many solutions
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