Let's eliminate x. To achieve this, mult. the 2nd equation by 2, obtaining
-8x + 2y = 10. Now add this result to the first equation:
8x-2y= -10
-8x + 2y = 10
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0
The two equations actually represent the same line. Without an x- or a y-value, we cannot solve for the value of the other variable. There are infinitely many solutions.
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